2018-19 "Post-Season Report" 4/23/19 West Central Montana avy conditions.

[Scott]

Avalanche Advisory for February 9, 2019

moderate danger
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A MODERATE avalanche danger exist for the West Central Montana backcountry. Developing winds and snowfall have increased the avalanche danger and will continue to do so through the day today, possibly rising to CONSIDERABLE on wind loaded terrain by this afternoon. Human triggered avalanches are possible this morning and will be trending up throughout the day today. Currently avalanches are confined to isolated terrain but will become more widespread.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Saturday, February 9th, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

An arctic air mass is moving across the forecast area today dropping temperatures and bringing strong easterly winds. The northern half of the region is already seeing the impacts of the arctic air with temperatures this morning ranging from -5 to -10 Fahrenheit. Winds are out of the ENE at 18 mph with gusts of 36 mph. Further south the winds are out of the SE at 9 mph and gusting to 16 mph. Temperatures for the southern half of the forecast area are 7 to 16 degrees F. Yesterday we received 1-3 inches of snow and overnight some locations received another 1-2 inches. SWE’s are low with the cold conditions and the falling snow is light and dry.

Wind slabs are the most likely type of avalanche of consequence to be triggered this morning. Winds picked up yesterday evening and have been building wind slabs overnight specifically for the northern portion of the advisory area. Winds are setting up out of the East again and will have unusual loading patterns. Cross loading will create hidden problems that are hard to identify and wind slabs will only grow in size and sensitivity to triggers as the day progresses.

Widespread loose snow avalanches avalanches will continue to be problematic specifically in areas with terrain traps that increase the consequences of a slide. The sluffs may develop into small storm slabs as more snow falls and builds the slab through the weekend. Similar to last weekend the new snow is very cold and dry, as additional snow is added to the snowpack keep an eye on how the new snow bonds to the old snow surface.

Keep in mind that as persistent slabs are gaining strength and have become less reactive, loading events like the one expected this weekend have the potential to re-activate weak layers. The layers of buried surface hoar are less widespread and reactive but should be considered today as they will be under increased stress. The facets near the ground are hopefully nearing the end of their activity as we have not been able to find them reactive for nearly a week.

Avalanche and Weather Outlook

Scattered snow showers will develop through the day today bringing an additional inch or two of snow by tonight. Strong easterly flow will sustain the strong winds. Temperatures look to drop further south as the arctic air continues to move south and west. A pattern of a few additional inches daily and cold temperatures looks to persist for the next week (forecast). Avalanche danger will be increasing specifically on wind loaded terrain today. The danger will slowly increase on all other terrain as well, as more snow is added to the snowpack over the weekend.

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.

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[Scott]

Avalanche Advisory for February 12, 2019

considerable danger
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The avalanche danger for the west central Montana backcountry is CONSIDERABLE. Dangerous avalanche conditions are present in our forecast area. Identify wind loaded slopes and avoid traveling on or under them. Human triggered avalanches are likely today, and natural avalanches are possible. Careful snowpack evaluation, cautious route-finding, and conservative-decision making are essential today.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 12, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 17 F to 24 F. In the Bitterroot winds are 6 mph with gusts of 10 mph out of the South. In the northern part of the advisory area, winds are 7 mph and gusting 16 mph out of the South. Snotels are reporting between .5 and 1.2 inches of SWE for the last 24 hours.

The primary avalanche problem today is wind drifted snow. Look for wind slabs on leeward slopes. Moderate to strong winds were cross loading some slopes, ridgetops, and creating large cornices. We got shooting cracks and saw a cornice fail naturally, all signs of instability. Look for wind deposits lower down on slopes with the strong winds and in unusual places. Identify these slopes and avoid traveling on them. (Video)

The second avalanche problem is new snow. Several new inches of snow has fallen in the forecast area. Look for large loose snow avalanches and storm slabs. We saw several point releases yesterday and saw the new snow start to slab up later in the day. Shooting cracks and natural avalanche activity are red flags of instability. Use small test slopes with low consequences to see how the new snow is bonding to old snow surfaces.

The final avalanche problem is persistent slabs. We have weak layers in our snowpack, buried surface hoar, and facets. Dig a pit 3 feet down and see if any of our weak layers are reactive in pit tests.

Bottom line: Dangerous avalanche conditions exist today. Avoid traveling on and under wind loaded slopes. New snow will be sensitive to human triggers. Use test slopes and lower angle terrain to check the bonding of new snow to old snow surfaces. Pay attention to changing conditions and look for red flags(shooting cracks, natural avalanche activity, collapsing, and new loading). Dig a pit 3 feet down to check for the dragons lurking(weak layers) in our snowpack.

Avalanche and Weather Outlook

Snow is predicted today and through the night. See the forecast here. With the predicted snow totals look for the avalanche danger to increase.

If you get out into the mountains, please share what you see on our public observations page. They are not only helpful to your community but extremely helpful to us.

Ski and ride safe.

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[Scott]

Avalanche Advisory for February 14, 2019

considerable danger
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The avalanche danger for the west central Montana backcountry is CONSIDERABLE on wind loaded slopes. All other slopes have a MODERATE danger. Identify wind loaded slopes and avoid them. Careful evaluation is needed to identify features of concern.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 14, 2019. Today’s advisory is sponsored by Yurtski. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 14 F to 20 F. In the Bitterroot winds are calm. In the northern part of the advisory area, winds are 6 mph and gusting 9 mph out of the ENE. Snotels are reporting between .3 and .7 inches of SWE for the last 24 hours.

Our forecast area has received several new inches of snow over the last 24 hours accompanied by moderate winds. The region will see rising temperatures today and no precipitation during the day.

The primary avalanche problem is wind drifted snow. Winds have loaded leeward slopes. Look for wind slabs on exposed terrain on northwest, northeast, and southeast aspects. These slabs are sensitive to human triggers. Look for smooth rounded pillows and drifts on ridges and cross-loaded slopes. Identify these slopes and avoid traveling on them.

The second avalanche problem is new snow. Look for large loose snow avalanches and storm slabs. We saw several point releases yesterday and saw the new snow start to slab up later in the day. Shooting cracks and natural avalanche activity are red flags of instability. Use small test slopes with low consequences to see how the new snow is bonding to old snow surfaces(video)(video).

The final avalanche problem is persistent slabs. We have weak layers in our snowpack, buried surface hoar, and facets. Dig a pit 3 feet down and see if any of our weak layers are reactive in pit tests.

Bottom line: Today the snowpack is adjusting to the new load of snow. Avoid wind drifted slopes. Dig a pit to see how the new snow is bonding to old snow surfaces and how the weak layers in our snowpack are adjusting to the new load of snow. Use test slopes and lower angle terrain to check the bonding of new snow to old snow surfaces. Pay attention to changing conditions and look for red flags(shooting cracks, natural avalanche activity, and collapsing).

Avalanche and Weather Outlook

Today, look for warming temperatures. The avalanche danger will stay the same today. Snow will enter the forecast area tonight with high snowlines in the Bitterroot. See the forecast here. New snow and wind will increase the avalanche danger overnight and into Friday.

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.





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[Scott]

Avalanche Advisory for February 15, 2019

considerable danger
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The avalanche danger for the west central Montana backcountry is CONSIDERABLE. Dangerous avalanche conditions are present in our forecast area. Identify wind loaded slopes and avoid traveling on or under them. Human triggered avalanches are likely today, and natural avalanches are possible. Careful snowpack evaluation, cautious route-finding, and conservative-decision making are essential today.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 15, 2019. Today’s advisory is sponsored by Yurtski. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 24 F to 32 F. In the Bitterroot winds are 16 mph with gusts of 24 mph out of the SW. In the northern part of the advisory area, winds are 7 mph and gusting 11 mph out of the NW. Snotels are reporting between .4 and .7 inches of SWE for the last 24 hours.

The primary avalanche problem is wind drifted snow. The advisory area experienced strong winds yesterday afternoon and through the night. Look for wind slabs on leeward terrain. These slabs are sensitive to human triggers. Look for smooth rounded pillows and drifts on ridges and cross-loaded slopes. Identify these slopes and avoid traveling on them.

The second avalanche problem is new snow. Heavier denser snow is falling on a variety of old snow surfaces. The new snow will need time to bond. Look for large loose snow avalanches and storm slabs. Shooting cracks and natural avalanche activity are red flags of instability. Use small test slopes with low consequences to see how the new snow is bonding to old snow surfaces.

The final avalanche problem is persistent slabs. We have weak layers in our snowpack, buried surface hoar, and facets. Dig a pit 3 feet down and see if any of our weak layers are reactive in pit tests.

Bottom line: The region has received a new load of heavier denser snow accompanied with strong winds. This combination has created dangerous avalanche conditions. The snowpack is adjusting to the new load of snow. Avoid wind drifted slopes. Dig a pit and see how the fresh snow is bonding and if the persistent weak layers are reactive in pit tests. Pay attention to changing weather conditions and avalanche conditions. Look for shooting cracks, natural activity, and collapses; these are clues to instabilities in the snowpack. Choose lower angle terrain(less than 30 degrees).

Avalanche and Weather Outlook

A cold front pushes in tonight. Snow is expected for today through Saturday. See the forecast here. New snow and wind will increase the avalanche danger.

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.

The post Avalanche Advisory for February 15, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory
Posted: Feb 16, 2019 06:24 am
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Missoula Avalanche
Avalanche Advisory for February 16, 2019

moderate danger
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The current avalanche danger is MODERATE for the West Central Montana Backcountry. Human triggered avalanches are possible on specific terrain and conditions have been in a constant state of change for the last few days. Carefully and continuously evaluate terrain and snowpack to identify areas of increased concern. The southern Missions and Southern Swan ranges have the potential to move to CONSIDERABLE later today as snow accumulates, but there is significant uncertainty in predicted snowfall.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Saturday, February 16th, 2019. Today’s advisory is sponsored by Yurtski. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

As of 5 am, this morning mountain temperatures range from 15 to 25 degrees Fahrenheit. Winds are out of the SW at 13 mph and gusting to 18 mph in the northern part of the region while winds in the southern Bitterroot are 3 mph with gusts to 9 mph from the SE. 24-hour snow totals range from 1-6 inches, and snotels have picked up an additional 0.1-0.5 inches of SWE.

Today, the new snow is a primary avalanche concern. The new snow can be problematic for a multitude of reasons. The first problem is storm slabs. The new snow is bonding well to the old snow surface at most locations and is gaining strength but needs another day or two to fully settle and bond. Secondly, the new snow sluffs easily and creates loose snow avalanches that can be dangerous if terrain traps are present. If the sun comes out and temperatures are mild be aware that small loose wet avalanches may develop later in the day.

Wind slabs are the second avalanche problem today. Winds have shifted back and forth and come and gone periodically over the last few days. Wind loading can be found on any aspect, but due to the variable nature of the winds, most wind slabs are relatively small and soft slabs. Look for signs of wind loading like rounded pillows of snow and cornices to identify what slopes have been loaded. More significant loading can be found at upper elevations and will have the potential for larger slabs.

Persistent slabs are still possible in isolated areas and are most prevalent in the southern portion of the advisory area. Facets and buried surface hoar can still be found in the southern Bitterroot. The persistent weak layers are continuing to gain strength slowly. Take a few minutes to dig a pit and perform stability tests to identify if persistent weak layers are present and reactive.

Big Picture: Given our recent weather, loading events and persistent weak layers lingering at some locations, there is plenty of reason to be suspicious of the snowpack. The snow is settling and bonding well but don’t forget to listen to your gut, if you have a feeling there is something you are missing you probably are. The snowpack requires attentive evaluation to gather all the pieces and clues in order to make an informed decision.

Avalanche and Weather Outlook

Today will bring scattered snowfall with accumulations of 1-3 inches at most locations. The caveats are the southern Missions and Swan ranges where more snow is possible today. However, there is a fair bit of uncertainty as to timing and total snowfall for the northern part of the forecast area. Stay aware of changing conditions and continually re-evaluate avalanche hazard throughout the day. A cold front is expected to move into the area tonight and bring increased wind and cold conditions again for Sunday. Avalanche hazard today will remain the same for the majority of the region. You can get the full forecast here.

If you make it out into the backcountry, let us know what you find on our public observations page.

Ski and ride safe.

The post Avalanche Advisory for February 16, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for February 17, 2019

considerable danger
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For the Southern Missions and Southern Swan ranges the avalanche danger is CONSIDERABLE. Human triggered avalanches are likely and natural avalanches are possible. For the Bitterroot and Rattlesnake mountains, the avalanche danger is MODERATE. Human triggered avalanches are possible with small avalanches in specific terrain and larger avalanches in isolated locations.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Sunday, February 17th, 2019. Today’s advisory is sponsored by Yurtski. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

The Southern Missions and Southern Swan ranges have received up to 8 inches of new snow since yesterday morning. Temperatures began dropping early this morning as a cold front is working its way across the region. Increasing easterly flow overnight from the frontal passage is further complicating issues in the area. Natural storm slab activity was reported yesterday afternoon outside of Seeley and faceted snow was easily failing under the new load in the southern Swan range (public observation). With increasing winds, wind drifted snow will continue to be a developing problem as the day progresses.

For the Rattlesnake and Bitterroot mountains, the likelihood of avalanches is lower. Temperatures are beginning to drop and easterly winds are increasing. Only 1-3 inches of new snow was seen for this portion of the advisory area. The primary avalanche concerns are wind slabs. Most wind slabs are still small and soft with the potential for larger wind slabs in isolated terrain, all of which will be growing today with strong Easterly flow. We received a report of skier triggered wind slabs in the central Bitterroot yesterday. In the southern Bitterroot, there are a few persistent weak layers that are gaining strength but still require cautious evaluation to determine if they are present and reactive as do some of the crust layers found throughout the region.

Big Picture: There is a significant amount of variability in the current avalanche conditions across our advisory area. Depending on where you travel today different concerns will be more prevalent than others. This means that you need to constantly evaluate conditions as they change across terrain, time, and space. Remember that the avalanche forecast condenses a lot of information and applies it to a broad area, but the final decision on what the hazard is for a single locale falls on your shoulders. The advisory is a great tool to help inform your decisions but when it comes to the end of the day it is ultimately up to you to determine what hazards are present and how reactive they are.

Avalanche and Weather Outlook

Temperatures will continue to fall and the forecast suggests strong wind and cold temperatures to be the dominant feature for the beginning of the week. Storm slab problems will begin settling but wind slab avalanche potential will be on the rise. Expect some hazards to be increasing while others decrease.

We received a bunch of public observations yesterday which is incredibly helpful to us as forecasters and the community as a whole. So thank you and keep them coming.

Ski and ride safe.

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[Scott]

Current West Central Montana Avalanche Advisory
Posted: Feb 19, 2019 06:38 am
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Missoula Avalanche
Avalanche Advisory for February 19, 2019

moderate danger
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The avalanche danger for the West Central Montana backcountry is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. With heightened avalanche conditions on specific terrain, carefully evaluate snow and terrain to identify features of concern.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday, February 19th, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Early this morning mountain temperatures are in the single digits with calm winds. Light snow yesterday brought an additional 1-2 inches of low-density snow and overnight isolated areas received an additional inch. Overall snow accumulation has been minimal and what areas have had flurries had very small increases in SWE, as not much loaded has been added to the snowpack.

Wind slabs are the first avalanche concern today. Small wind slabs can be found on most aspects near ridges and summits. They are gaining strength but can still be reactive and will continue to pose a notable hazard. Larger wind slabs are possible at some locations under the right conditions. We observed a sizeable skier triggered wind slab (video) (pic) and found some wind affected areas had propagations in stability tests. These were occurring in locations where cold storm snow is preserved under a wind slab.

Persistent weak layers can be found throughout the forecast area and some are more prevalent at locations than others. Facets that formed during the earlier cold snap are less reactive but still present and concerning. Buried surface hoar can be found in isolated locations and is less reactive but well preserved at some locations and should give you pause (pic). Similarly, faceted snow and depth hoar near the ground is not very reactive but would result in very large avalanches (video). Although the likelihood of triggering them is low the consequences are very high. Be wary of slopes with persistent weak layers.

Bottom line: Widespread small wind slabs exist, bigger wind slabs are possible in isolated terrain that has the right recipe. Small persistent slabs are possible and very large persistent slabs are unlikely but not to be trifled with. Determining what problem is the greatest concern on a given slope can be challenging right now. Carefully evaluate the snowpack and perform stability tests to identify what layers are present and reactive before committing to a slope.

Avalanche and Weather Outlook

The weather forecast for today looks to be continued calm and cold. Snowfall will develop tonight but totals are unclear and could be anywhere from 1-7 inches. Winds will also trend up as a weak arctic air mass impacts the region. Avalanche danger will likely increase overnight tonight as areas of surface hoar that formed during the night last night will get buried by the new snow. Cold will persist through the week with multiple rounds of snow.

There has been an increase in public observations lately, which is invaluable to us as forecasters and a great resource for our community. Keep sharing what you are finding.

Ski and Ride Safe.

The post Avalanche Advisory for February 19, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Current West Central Montana Avalanche Advisory
Posted: Feb 21, 2019 06:50 am
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Missoula Avalanche
Avalanche Advisory for February 21, 2019

moderate danger
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The avalanche danger for the west central Montana backcountry is MODERATE. Heightened avalanche conditions are present on specific terrain. Carefully evaluate snowpack and terrain to identify areas of increased hazard. Human triggered avalanches of varying size are possible.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Thursday, February 21st, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Most locations have received 1-2 inches of snow in the past 24 hours while a few locations got up to 4 inches. Winds are developing out of the NE at 6 mph with gusts up to 20 mph. Mountain temperatures range from -3 to 12 degrees this morning.

There are a number of different problems that are possible depending on the mountain range, aspect, and elevation. To help understand the multitude of problems we will discuss and order them in regards to size. Small loose wet avalanches are possible to likely. The loose wet slides will be focused on solar aspects and will become more active with increased sun later in the day. If roller-balls start to develop, move to a cooler aspect to avoid getting carried into terrain traps by wet and heavy snow.

Small pockets of wind drifted snow have created soft wind slabs that can be found on just about every aspect. Due to the variable winds, the smaller wind slab can be hard to identify especially in terrain that is cross loaded. Slightly larger than these wind slabs are a persistent slab. Facets just below the storm snow are not overly reactive due to the lack of a slab overlying them but warrant evaluation. Buried surface hoar can be found on the uppermost crusts at some locations and will be a concern until the crystals break down further. The persistent weak layers near the surface appear to be concentrated in the Bitterroot range or locations with shallower snow.

Large Wind slabs are possible in isolated areas. Reports of larger wind slabs continue to roll in but are occurring in single couloirs or isolated slopes with no consistent aspect but tend to be concentrated at upper elevations or just below ridges. Larger wind slabs are also more reactive when they are overlying cold preserved storm snow that fell earlier this month.

Very large persistent slabs are unlikely but could easily be triggered as a step-down avalanche. Surface hoar that formed in mid-January as a bathtub ring can be found well preserved and still very large on cold and shaded aspects below approximately 6,000 feet. If this layer is initiated it will propagate easily and create very dangerous avalanches (video). Large to very large avalanches are unlikely on facets near the ground or depth hoar. Similarly, the deep facets are unlikely to trigger but under the right circumstances could be activated in a step-down avalanche which would be scary, to say the least. These layers won’t give you any red flag warning and can only be identified by digging a pit and performing stability tests. If you find deep BSH or Facets with any other signs of weakness above them seriously consider the consequences of these deep layers failing.

Bottom line: Right now, avalanches of varying size and problem can be found on nearly any aspect or elevation. Even with a moderate danger, this means that you have to be on your game. Observe conditions carefully, to identify what problems are present and where.

Avalanche and Weather Outlook

Light snow showers are possible today producing minimal accumulations of snow. Light to moderate winds are forecasted out of the NE which will shift to the SW tonight as the next round of snow sets up for this weekend (Forecast). Avalanche danger will remain the same through the day today and into tomorrow.

There has been an increase in public observations lately, which is invaluable to us as forecasters and a great resource for our community. Keep sharing what you are finding.

Ski and ride safe.

The post Avalanche Advisory for February 21, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for February 23, 2019

moderate danger
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The avalanche danger early this morning is MODERATE but will shift towards CONSIDERABLE as the day progresses. This morning, human triggered avalanches are possible but will trend towards likely as the new snow stresses the snowpack and new problems develop. Dangerous avalanche conditions will emerge and will require careful snowpack evaluation, cautious route-finding and conservative decision making.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Saturday, February 23rd, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Over the last 24 hours, the forecast area has picked up 3 to 6 inches of new low-density snow. The fresh snow has added 0.2-0.5 inches of SWE. Mountain temperatures as of 4 am this morning are in the teens. The winds are 6 mph with gusts up to 16 mph from the SE in the southern Bitterroot and primarily S in the northern region of the advisory area.

Persistent slabs are a significant concern today. A layer of surface hoar is getting buried by the new snow and will become reactive as a slab forms over this weak layer. There are other layers of buried surface hoar that were gaining strength but will be under more stress with the new load of snow. A layer of cold preserved storm snow is still suspect and can be reactive at some locations; this layer is hard to identify but can be found when performing stability tests. Faceted snow has the potential to become more responsive with the new load as does the depth hoar, although it is deep an unlikely to be triggered except in a step-down avalanche.

Winds have mostly been light but ramped up to moderate strength for a few hours yesterday evening. Wind slab development occurs much faster so the small wind slabs likely grew overnight. There is plenty of snow for transport and in areas with more powerful winds look for growing wind slabs. Larger wind slabs are possible in bigger terrain like high elevation bowls and below summit ridges. The variable winds have again made it difficult to identify all terrain that is loaded, and there is a significant amount of cross loaded terrain right now. Be on the lookout for any signs of wind loading and stay aware of conditions as the change through the day today.

Loose snow avalanches will easily be triggered in steep terrain today. The new snow is light and will sluff readily. Avoid terrain traps as they increase the consequences of getting knocked off your feet or sled and going for a ride. The loose surface snow will become more problematic as more snow is added over the weekend and starts to form a slab creating new widespread storm slabs.

Avalanche and Weather Outlook

Snowfall has slowed this morning, but an additional 2-4 inches of low-density snow are expected today. Winds should build and shift to the E-NE and begin to redistribute the new low-density snow. Another round of snow is setting up for tonight into Sunday. With increased wind and snow the avalanche danger will continue to trend upwards.

Bottom Line: A good dose of new snow and strengthening winds will easily push the avalanche danger to CONSIDERABLE. The question is when do the scales tip? Some locations will get there faster than others, either because of more load or due to the freshly buried layer of surface hoar. Stay vigilant in the backcountry today and continue to evaluate conditions as they change, watch for growing signs of instability like collapsing, shooting cracks, whumphing, and natural avalanche activity. Human triggered avalanches will become likely so utilize conservative decision-making to avoid finding the tipping point and getting caught in a slide.

Feel free to share what you find in the backcountry on our Public Observation page. It’s a great resource for us and the whole backcountry community.

Ski and ride safe.

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[Scott]

Avalanche Warning for February 25, 2019

high danger
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An avalanche warning is in effect for backcountry terrain in the Bitterroot mountains. The current avalanche danger is HIGH from Granite Pass south to Lost Trail Pass. Very dangerous avalanche conditions exist. Travel in and around avalanche terrain is not recommended. For the rest of the forecast area, the avalanche danger is CONSIDERABLE.

This is Logan King with an avalanche warning for Monday, February 25th, 2019. This avalanche warning is valid for 24 hours. The avalanche warning will either be extended or terminated at 0600 on February 26th.

This danger rating does not apply to operating ski areas and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

The Bitterroot mountains have accumulated 6-16 inches of new snow with southerly winds in the teens gusting to the twenties. The northern portion of the forecast area has received 2-6 inches of snow with strong Easterly winds of 10 mph with gusts into the twenties.

A hefty load of new snow has created dangerous avalanche conditions for the Bitterroot mountains. Weak layers of snow that are now buried under the new slab will be reactive with the increased load. Human triggered avalanches are likely and will be large in many areas. Avoid traveling in or near avalanche terrain today.

For the Southern Swans, Southern Missions and the Rattlesnake mountains a CONSIDERABLE avalanche danger exists. Human triggered avalanches are likely. Look for red flag warnings like cracking, collapsing, whumphing and natural activity to identify areas of heightened concern. Careful snowpack evaluation, cautious route-finding and conservative decision making are essential for backcountry travel in these mountain ranges today.

Avalanche and Weather Outlook

Avalanche danger will continue to trend upwards as accumulating snow persists through the day and into tomorrow. More snow is expected to total between 7-14 inches for the northern part of the forecast area while the Bitterroot will continue to take the brunt of the storm with an additional 15-20 inches of snow expected by tomorrow. (Forecast)

Please feel free to share any observations on our Public Observations Page.

Ski and Ride Safe.

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[Scott]

Avalanche Warning for February 26, 2019

high danger
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An avalanche warning is in effect for backcountry terrain in the Bitterroot mountains from Granite Pass south to Lost Trail Pass and the Rattlesnake Mountains. The current avalanche danger is HIGH. Very dangerous avalanche conditions are present. Travel in avalanche terrain is not recommended today. Avoid runout zones. Human triggered avalanches are very likely, and natural avalanches are likely. In the southern Missions and southern Swan, the avalanche danger is CONSIDERABLE.

This is Travis Craft with an avalanche warning for Tuesday, February 26, 2019. This avalanche warning will expire at 6:00 am on February 27, 2019. The warning will either be extended or terminated at that time.

This danger rating does not apply to operating ski areas and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from -3 F to 18 F. In the Bitterroot winds are 9 mph with gusts of 15 mph out of the West. In the northern part of the advisory area, winds are 3 mph and gusting 8 mph out of the NE. Snotels are reporting between .9 and 1 inches of SWE for the last 24 hours.

The storm totals have favored the Bitterroot mountains and the Rattlesnake. Between 12 and 20 inches have fallen in these ranges over the last 24 hours. Very dangerous avalanche conditions are present. Travel in avalanche terrain is not recommended today. Avoid runout zones. Human triggered avalanches are very likely, and natural avalanches are likely.

The southern Mission and southern Swan ranges have a CONSIDERABLE avalanche danger.

The new snow will take time to bond to old snow surfaces. Winds have created sensitive wind slabs on leeward terrain. The new snow has buried weak layers and is stressing old buried weak layers. Yesterday, we were able to trigger small test slopes very easily and got shooting cracks from our machines and skies on flat ground. We saw natural activity on slopes that had wind drifted snow on them. We got reports of shooting cracks that were propagating very long distances.

Avalanche and Weather Outlook

Today light snow accumulations and moderate winds. See the forecast here. The avalanche danger will remain the same.

Please feel free to share any observations on our Public Observations Page.

Ski and Ride Safe.

The post Avalanche Warning for February 26, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for February 27, 2019

considerable danger
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The Avalanche warning is terminated. The avalanche danger for the west central Montana backcountry is CONSIDERABLE. Dangerous avalanche conditions are present. Look for the avalanche danger to increase throughout the day, possibly going to HIGH on wind loaded slopes by the afternoon.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 27, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 4 F to 16 F in the region. In the Bitterroot winds are 9 mph with gusts of 12 out of the SSE. In the northern part of the advisory area, winds are 7 mph and gusting 21 mph out of the East. Snotels are reporting between .1 and .2 inches of SWE for the last 24 hours.

Yesterday allowed the snowpack to adjust to the weight of the new snow. Winds have loaded leeward slopes.

The primary avalanche problem is wind drifted snow on leeward slopes. Shifting winds have deposited snow in unusual spots. Look for wind slabs on cross-loaded slopes and ridges. Pay attention to slopes at low and mid elevations which have been wind loaded. Identify these slopes and avoid traveling on them. These slabs will be sensitive to human triggers today.

The second problem is persistent slabs. The storm dropped a significant load of snow on our buried weak layers. These layers are guilty until proven innocent. Dig a pit that is 4 feet down and see if buried surface hoar is present and reactive. Look for shooting cracks, natural activity, and collapses; these are clues to instabilities in the snowpack.

The last avalanche problem is storm slabs. The forecast area has received a significant amount of new snow from the last storm. The snowpack is adjusting to the new load. Shooting cracks and natural avalanche activity are red flags of instability. Use small test slopes with low consequences to see how the new snow is bonding to old snow surfaces.

Bottom line: Dangerous avalanche conditions exist today. Avoid traveling on and under wind loaded slopes. New snow will be sensitive to human triggers. Use test slopes and lower angle terrain to check the bonding of new snow to old snow surfaces. Pay attention to changing conditions and look for red flags(shooting cracks, natural avalanche activity, collapsing, and new loading). Dig a pit 4 feet down to check for the dragons lurking(weak layers) in our snowpack. Choose lower angle terrain(less than 30 degrees).

Avalanche and Weather Outlook

Snow today accompanied with wind. See the forecast here. New snow and wind will increase the avalanche danger. Pay attention to changing weather conditions and avalanche conditions. Look for shooting cracks, natural activity, and collapses; these are clues to instabilities in the snowpack. Choose lower angle terrain(less than 30 degrees).

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.

The post Avalanche Advisory for February 27, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for February 28, 2019

considerable danger
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The avalanche danger for the west central Montana backcountry is CONSIDERABLE. Dangerous avalanche conditions are present in our forecast area. Identify wind loaded slopes and avoid traveling on or under them. Human triggered avalanches are likely today, and natural avalanches are possible. Careful snowpack evaluation, cautious route-finding, and conservative-decision making are essential today.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 28, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 18 F to 30 F. In the Bitterroot winds are 10 mph with gusts of 15 mph out of the SSE. In the northern part of the advisory area, winds are 5 mph and gusting 7 mph out of the NE. Snotels are reporting between .4 and .9 inches of SWE for the last 24 hours.

The southern Missions, southern Swans, and Rattlesnake mountains primary avalanche problem is wind slabs. Yesterday, we got easy propagations in pit tests on wind drifted terrain(video). Natural avalanches released in the last 24 hours. Look for wind slabs on cross-loaded slopes and ridges. Pay attention to slopes at low and mid elevations which have been wind loaded. Identify these slopes and avoid traveling on them. These slabs will be sensitive to human triggers today.

The primary avalanche problem in the central and southern Bitterroot is new snow. Look for large loose snow avalanches and storm slabs. Use small test slopes with low consequences to see how the new snow is bonding to old snow surfaces. The sluffs are very big and in steep terrain could be a problem especially if it takes you into a terrain trap(cliffs, rock bands or trees).

The second avalanche problem for the forecast area is persistent slabs. The storm dropped a significant load of snow on our buried weak layers. These layers are guilty until proven innocent. Dig a pit that is 4 feet down and see if buried surface hoar is present and reactive. Look for shooting cracks, natural activity, and collapses; these are clues to instabilities in the snowpack.

Bottom line: Dangerous avalanche conditions exist today. Avoid traveling on and under wind loaded slopes. New snow will be sensitive to human triggers. Use test slopes and lower angle terrain to check the bonding of new snow to old snow surfaces. Pay attention to changing conditions and look for red flags(shooting cracks, natural avalanche activity, collapsing, and new loading). Dig a pit 4 feet down to check for the dragons lurking(weak layers) in our snowpack.

Avalanche and Weather Outlook

Light snow showers and strong winds today. See the forecast here. This weather will increase the avalanche danger by loading leeward terrain.

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.

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[Scott]

The avalanche danger is CONSIDERABLE for the west central Montana backcountry on wind loaded slopes. Strong winds and significant snow are creating dangerous avalanche conditions, making human-triggered avalanches likely on leeward slopes. All other slopes the danger is MODERATE. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential for travel in the backcountry today.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 02, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from -10 F to 20 F in the region. In the Bitterroot winds are 1 mph with gusts of 7 mph out of the WNW. In the northern part of the advisory area, winds are reading 9 mph with gusts of 24 mph out of the ENE. The forecast area received 1 to 4 inches of new snow in the last 24 hours.

The primary avalanche problem is wind drifted snow. Leeward terrain wind loaded overnight. Look for shooting cracks from skis or machine to identify instabilities. Look for rounded pillows of snow near ridges and on cross-loaded slopes. Pay attention to slopes at low and mid elevations which have been wind loaded. Identify these slopes and avoid traveling on them. Recognize signs of instability such as cracking in the surface snow. It is possible to cause a slab avalanche on wind loaded terrain today.

The secondary avalanche problem is new snow. Look for large loose snow avalanches and storm slabs. Use small test slopes with low consequences to see how the new snow is bonding to old snow surfaces. The sluffs are very big and in steep terrain could be a problem especially if it takes you into a terrain trap(cliffs, rock bands or trees).

Bottom line: Avoid wind loaded slopes today. Use test slopes to see how the new snow is bonding to old snow surfaces. Dig a pit 4 feet down and check for any buried weak layers.

Missoula Foot Hills/Mt. Jumbo/Mt. Sentinel

There are slopes around town people are skiing. Respect closures on Mt. Jumbo. There are unstable conditions present on certain slopes. Take extra caution to what is below you and if you were to trigger an avalanche what are the consequences.

Avalanche and Weather Outlook

Strong winds and cold temperatures will continue through the weekend. Look for the avalanche danger to remain the same. See the forecast here.

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.



The post Avalanche Advisory for March 2, 2019 appeared first on Missoula Avalanche

 

[Scott]

Avalanche Advisory for March 2, 2019

considerable danger
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The avalanche danger is CONSIDERABLE for the west central Montana backcountry on wind loaded slopes. Strong winds and significant snow are creating dangerous avalanche conditions, making human-triggered avalanches likely on leeward slopes. All other slopes the danger is MODERATE. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential for travel in the backcountry today.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 02, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from -10 F to 20 F in the region. In the Bitterroot winds are 1 mph with gusts of 7 mph out of the WNW. In the northern part of the advisory area, winds are reading 9 mph with gusts of 24 mph out of the ENE. The forecast area received 1 to 4 inches of new snow in the last 24 hours.

The primary avalanche problem is wind drifted snow. Leeward terrain wind loaded overnight. Look for shooting cracks from skis or machine to identify instabilities. Look for rounded pillows of snow near ridges and on cross-loaded slopes. Pay attention to slopes at low and mid elevations which have been wind loaded. Identify these slopes and avoid traveling on them. Recognize signs of instability such as cracking in the surface snow. It is possible to cause a slab avalanche on wind loaded terrain today.

The secondary avalanche problem is new snow. Look for large loose snow avalanches and storm slabs. Use small test slopes with low consequences to see how the new snow is bonding to old snow surfaces. The sluffs are very big and in steep terrain could be a problem especially if it takes you into a terrain trap(cliffs, rock bands or trees).

Bottom line: Avoid wind loaded slopes today. Use test slopes to see how the new snow is bonding to old snow surfaces. Dig a pit 4 feet down and check for any buried weak layers.

Missoula Foot Hills/Mt. Jumbo/Mt. Sentinel

There are slopes around town people are skiing. Respect closures on Mt. Jumbo. There are unstable conditions present on certain slopes. Take extra caution to what is below you and if you were to trigger an avalanche what are the consequences.

Avalanche and Weather Outlook

Strong winds and cold temperatures will continue through the weekend. Look for the avalanche danger to remain the same. See the forecast here.

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.

 

[Scott]

Avalanche Advisory for March 5, 2019

low danger
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The current avalanche danger for the West Central Montana backcountry is LOW. Low danger does not mean no danger! Be on the lookout for avalanches in isolated or extreme terrain.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 05, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 1 F to 10 F in the region. In the Bitterroot winds are 14 mph with gusts of 20 mph out of the SE. In the northern part of the advisory area, winds are reading 1 mph with gusts of 6 mph out of the SE. The forecast area received new snow overnight.

Overall our snowpack is gaining strength. We have not had any natural or skier triggered avalanches on our buried weak layers in the last week. Pit tests are not propagating on buried surface hoar or facets near the ground. Wind slabs are gaining strength and are very hard to trigger. Storm slabs are settling out and bonding. Overall the snowpack is stable.

The primary avalanche problem is loose dry snow on sheltered aspects. These should not be much of a problem unless they knock you off your feet or machine and take you into a terrain trap.

Bottom line: The snowpack has gained strength. You can find places where shallow snow sits on weak facets on the ground and more likely to trigger an avalanche. Those places our at lower elevations in sheltered spots, near rock bands and cliffs. Dig a pit 4 feet deep to assess the snowpack and check for any buried weak layers. Use safe travel protocols, only one person on a slope at a time. Give cornices a wide berth; they break father back than anticipated.

The avalanche danger continues to trend downward and is rated at low. I will say it again; Low danger does not mean no danger! It is a stout low right now and avalanches are possible if you are in the wrong place at the wrong time. Carefully evaluate the likelihood and potential consequences of avalanches before committing to avalanche terrain. Don’t treat the low rating as a green light and jump straight into big terrain, start on smaller slopes with lower consequences and test the snow before going for a big line. Stay aware of changing conditions and continue to utilize safe travel protocols and don’t but lulled into complacency.

Missoula Foot Hills/Mt. Jumbo/Mt. Sentinel

There are slopes around town people are skiing. Respect closures on Mt. Jumbo. There are unstable conditions present on certain slopes. Take extra caution to what is below you and if you were to trigger an avalanche what are the consequences.

Avalanche and Weather Outlook

Temperatures warm today and a system moves in on Wednesday with small amounts of moisture. Look for the avalanche danger to increase. See the forecast here.

As always, if you make it out, please, feel free to share, what you find on our public observations page.

Ski and ride safe.

 

[Scott]

Avalanche Advisory for March 7, 2019

moderate danger
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A MODERATE avalanche danger exists today for the West Central Montana backcountry. Heightened avalanche conditions exist on wind loaded terrain above 5,500 feet and at locations with shallow snowpacks. Human triggered avalanches are possible and careful evaluation is necessary to identify areas of heightened concern.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Thursday, March 7th, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Over the past 24 hours, 2-6 inches of snow have fallen across the forecast area adding an additional .2-.5 inches of SWE. Temperatures as of 4 am are just below freezing. Winds are light in the north at 5 mph and gusting to 8 mph from the ENE and are slightly stronger to the south at 11 mph gusting to 1 mph from the SSE.

Above 5,500 feet the primary avalanche concern is wind slabs. Winds have created pockets of isolated slabs that are generally small but can pack a punch as they can release with a lot of energy. Wind slabs are sitting on weak faceted snow and are now buried under a few inches of new snow making them harder to identify but still primed for a trigger. Larger wind slabs are possible but are isolated and less reactive. Persistent slabs and deep persistent slabs are also possible at upper elevations in isolated locations. In the rattlesnake, yesterday areas with shallow snow were found to have extensive faceting and were failing readily in stability tests (Video). Widespread faceting has occurred throughout the snowpack but is only reactive at some locations. Deep instability is not widespread but if found will result in very large avalanches that have high consequences.

At lower elevations persistent weak layers are widespread but lack the slab overlying the weaknesses to produce avalanches at most locations. Although weak faceted snow can be found on any slope, it is only reactive under the right circumstances. Locations where a denser or stiff slab overlying facets will be susceptible to triggers for the foreseeable future. The only way to know if the persistent weak layers are reactive is to perform stability tests in pits and on test slopes. Wind loading is very isolated at lower elevations and can primarily be found near channeling corridors and major valleys. These areas will be the likely trigger points as they will have the structure required to propagate a failure for a slab avalanche.

Human triggered avalanches are possible today. If you are in the wrong place at the wrong time it will be easy to trigger a slide. Avalanches will generally be small but a few have the potential to be large with high consequences. Remember that Moderate and Low danger doesn’t mean that things are “safe”. The conditions right now are a great example of the fact that there are places you can and will trigger avalanches during Moderate danger and you have to carefully assess conditions and terrain to identify areas and features of heightened concern.

Avalanche and Weather Outlook

Light snow showers are expected today with a brief break tonight. Continued light and scattered snow is forecasted through Friday and Saturday. Winds will shift directions and complicated wind loading today and into the weekend. Surface hoar formed at many locations earlier this week and has been knocked down at some locations but can now be found in certain areas. The newly buried surface hoar will become more reactive as more load is added on top of this very weak layer. Overall the avalanche danger should remain the same without any major changes in the forecast.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

The post Avalanche Advisory for March 7, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for March 9, 2019

moderate danger
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The current avalanche danger is MODERATE for the West Central Montana backcountry. Small winds slabs are possible on wind drifted terrain, and large stubborn wind slabs over weak snow or deep large avalanches are possible in isolated locations. Carefully evaluate terrain and the snowpack to identify locations where hazards exist.

Good morning, this is Logan King with the West Central Montana Avalanche Center’s avalanche advisory for Saturday, March 9th, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Winds this morning are light out of the SW to WSW. Mountain temperatures are around 10 degrees Fahrenheit as of 4 am. Most locations picked up a trace to 1 inch of snow over the past 24 hours but due to the scattered and showery nature of the flurries, some locations have received up to 2-4 inches of snow.

Small wind slabs that are only a few inches thick can release with high energy and carry a person into terrain traps. Look for any signs of wind loading like sastrugi and cornices to determine what slopes have been loaded keeping in mind that wind slabs are likely obscured under the trace to few inches of snow that we have seen over the last couple of days. Larger wind slabs are possible at upper elevations near ridgelines or on open cross-loaded terrain and will be most reactive in locations where they formed over weak faceted snow. Many locations have experienced winds shifting back and forth from east and west, making wind slabs possible on any slope with significant local variability.

There is a lot of faceted and weak snow throughout the advisory area. Most of which is unreactive except when a denser slab is overlaying the weak layer (wind slabs). However, the greatest persistent slab concern is deep persistent slabs. In isolated locations with shallow snowpacks above 6,000 feet, large-grained facets near the ground can fail (Video). The avalanches failing on depth hoar will be big and have serious consequences. This problem is not widespread and hard to pinpoint unless you dig a pit to identify how deep the snowpack is and if depth hoar is present and reactive.

Loose wet avalanche activity is increasing as the days get longer and solar radiation increases. Surface crusts can be found on solar aspects to about mid-elevations, but with more sun and warmer temperatures (still below average), the crusts will continue to move upslope. With crust development, the melt-freeze process will produce diurnal cycles of loose wet avalanches. On the southern half of the compass and in steep terrain expect to see rollerballs forming by midday and leading to loose wet sluffs. These avalanches are small and slow-moving but can easily injure a person or become dangerous if terrain traps are present.

Avalanche and Weather Outlook

Mostly clear skies will be interrupted by scattered snow showers through the day today. Snowfall will be light and sporadic with minimal accumulation. Light winds will continue, predominantly out of the SW. The avalanche danger will remain the same through the weekend until a shift occurs in the weather which looks to be setting up for mid-week (forecast)

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

The post Avalanche Advisory for March 9, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for March 12, 2019

moderate danger
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The avalanche danger is MODERATE for the west central Montana backcountry. It is still possible to trigger a small wind slab at lower elevations and a large wind slab at higher elevations. It is possible to trigger a very large avalanche in isolated areas in a shallow snowpack on depth hoar. Carefully evaluate terrain and the snowpack to identify locations where hazards exist.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 12, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 19 F to 23 F in the region. In the Bitterroot winds are 12 mph with gusts of 18 mph out of the SSE. In the northern part of the advisory area, winds are reading 11 mph with gusts of 24 mph out of the S. No new snow in the last 24 hours.

The primary avalanche problem today is wind slabs. There are small wind slabs located on leeward slopes at lower elevations(>7000 ft). On ridges and at high elevations you can find large wind slabs(Video).

There is a lot of faceted and weak snow throughout the advisory area. Most of which is unreactive except when a denser slab is overlaying the weak layer (wind slabs). However, the greatest persistent slab concern is deep persistent slabs. In isolated locations with shallow snowpacks above 6,000 feet, large-grained facets near the ground can fail ( public observation, Video, Video). The avalanches failing on depth hoar will be big and have serious consequences. This problem is not widespread and hard to pinpoint unless you dig a pit to identify how deep the snowpack is and if depth hoar is present and reactive.

Bottom line: It is still possible to trigger an avalanche today on wind loaded slopes or in places with a shallow snowpack with a weak layer. Over the weekend a small slab was skier triggered on a slope near a rock band in a shallow snowpack in the Rattlesnake(observation). Dig a pit, see how deep the snowpack is and if there are any layers of concern that are reactive in pit tests. Cornices are getting weaker, and we saw evidence of natural releases with the warmer temperatures. Pay attention to changing conditions as you switch aspects. The snowpack is variable right now.

Avalanche and Weather Outlook

Snow showers enter the region today and into Wednesday. The addition of new snow and winds will not increase the avalanche danger. See the forecast.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

The post Avalanche Advisory for March 12, 2019 appeared first on Missoula Avalanche.

 

[Scott]

Avalanche Advisory for March 14, 2019

moderate danger
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The avalanche danger is MODERATE for the west central Montana backcountry. It is possible to trigger a slide on persistent weak layers in our snowpack. Look for wet loose activity to increase throughout the day on sun-exposed slopes. Carefully evaluate terrain and the snowpack to identify locations where hazards exist.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 14, 2019. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 13 F to 20 F in the region. In the Bitterroot winds are 8 mph with gusts of 13 mph out of the W. In the northern part of the advisory area, winds are reading 7 mph with gusts of 9 mph out of the SW. The advisory area received 2-8 new inches of snow in the last 24 hours.

The primary avalanche problem is persistent weak layers. On shaded and protected slopes the new snow buried surface hoar. The buried surface hoar is very sensitive to triggers(video). This layer is hard to find and the only way to find it is to dig in the snow and see if it is there. Look for this layer on relatively cold and sheltered aspects. In isolated locations with shallow snowpacks above 6,000 feet, large-grained facets near the ground can fail ( public observation, Video, Video). The avalanches failing on depth hoar will be big and have serious consequences.

The second avalanche problem is loose dry on sheltered aspects and loose wet on solar aspects. Yesterday on slopes that had melt-freeze crusts on them, loose dry avalanches were very easy to trigger and in areas of the advisory area that received 8 inches of snow, southern Bitterroot and Rattlesnake, were large and could defiantly knock you of your skis or machine(picture). Today as temperatures rise and the sun comes out look for loose wet activity to increase on sun-exposed slopes.

Bottom line: Use small test slopes to see how the new snow bonded to old snow surfaces. Dig a pit to check for any buried surface hoar on sheltered aspects. Use probe and ski pole tests for checking for shallow snowpacks that harbor weak snow near the ground. Look for roller ball activity on solar aspects and change aspects to colder ones as the snow surface gets saturated.

Avalanche and Weather Outlook

We are entering a period of warming. Look for possible snow showers on Sunday but by next week look for high and dry conditions. See the forecast. This weather should not increase the avalanche danger.

If you get out into the backcountry, please share your observations on our public observation page.

Ski and ride safe.

The post Avalanche Advisory for March 14, 2019 appeared first on Missoula Avalanche.