2019-20 West Central Montana Avalanche Conditions---!!! CONSIDERABLE !!!---3/31/2020

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Here are the 2019-20 West Central Montana Avalanche updates.
Please view the most recent report in the last post of this thread.
I leave all reports in this thread for the season, so you can study the condition trends throughout the season.
I will update as I can.
 
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Greetings From Missoula Avalanche
Winter is just around the corner, and the biggest backcountry event in the region is coming up. The 13th Annual Pray For Snow Party will be held on Friday, October 4th from 5-10 pm at the Caras Park Pavillion in Missoula, Montana. If you have been to the party in the past, you know that it is an excellent evening of food, drink, live music, gear raffle, fun, and more. All proceeds from this event help pay for the avalanche forecasting and education programs you need to make wise decisions in the backcountry and come home safely each day.

The 13th Annual Pray For Snow Party is not only the single largest fundraiser for the West Central Montana Avalanche Center. It's a chance for us to all come together as a community, get to know each other, and celebrate the upcoming season. This fundraiser couldn't happen without all the amazing groups who donate goods and services. Together we're here to help everyone get out, have fun, and come home safe! Thanks for showing your support and helping us to continue our mission.
 

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Avalanche Special Update – Early Season Update – September 27, 2019

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This is Logan King with an early season update for the West Central Montana Avalanche center. The calendar just officially switched over to fall but a significant winter storm is already on the horizon. Early season snow may be getting some folks excited. Skis and sleds may be coming out of the garage, but it’s important to remember that if there is enough snow to ride, then there is enough snow to slide! Avalanche preparedness starts now and even though it is early in the season, you need to stay aware of the potential for avalanches. Early season snowfall creates the greatest hazard at upper elevations and tends to be concentrated to wind loaded terrain where more snow will be found. Keep in mind that there are increased consequences of even small slides this time of year due to exposed rocks, cliffs, and stumps that raise the potential for trauma. Keep an eye on the weather as this early season snow may lead to avalanche problems that can persist for the entire season. Now is the time to start the process of watching the weather and observing how the terrain begins to fill in. If you are interested in learning more, avalanche education opportunities will be posted next week and opening for enrollment. We look forward to another great season and hope to see you at the Pray for Snow on October 4th from 5-10pm at Caras Park.
Remember, avalanches don’t care if you are skiing, climbing, sledding, hunting or just taking your dog for a walk…if there is snow on the ground consider the potential and consequences of an avalanche before you enter steep terrain.
The post Avalanche Special Update – Early Season Update – September 27, 2019 appeared first on Missoula Avalanche.
This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide to help you make more informed decisions regarding travel in avalanche terrain for the next few days.

Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to Hoodoo Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information for the Lookout Pass/St. Regis Basin is available from the Idaho Panhandle Avalanche Center.
 

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Avalanche Special Update – Early Season Update – November 26, 2019

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This is Travis Craft with an early season snowpack update, on November 26, 2019.
We want to convey our sincere thanks to the volunteers, board members, sponsors, and everyone who joined us at the 13th annual Pray For Snow Party! Our major fundraising event of the year was a success! The funds raised will help cover the expenses for the avalanche forecasts and education programs for the region. Again, thank you for your continued support.
A melt-freeze base exists in the upper elevations (7000’+) of the northern forecast area (Mission, Swan, and Rattlesnake). A significantly thinner snowpack exists in the southern forecast area (Bitterroot). Upper elevation snow has gone through several melt-freeze cycles, and rain on 11/17 reached up to 9000′. In some areas, rain and melt-freeze crusts are exposed, resulting in “slide-for-life” conditions. Icy, slick crusts present an objective hazard to travelers and have created a very slick interface/bed surface for future avalanches.
New snow has been trickling in, up to several inches in the upper elevations. Moderate to strong winds have been transporting this snow and creating wind slabs on leeward terrain. Wind slabs are the primary avalanche concern, up to D2 in size (large enough to bury, injure, and/or kill a person).
New snow is the secondary avalanche concern. Loose snow avalanches are most likely. However, storm slabs may form if we receive more snow than what is currently forecast. The slick bed surface could make storm slabs very reactive to human triggering. Assess conditions and reactivity throughout travel; use formal (compression and extended column) and informal tests (hand shears, small test slopes). Pay attention to red flag data.
  • Recent avalanche activity
  • Cracking or collapsing snowpack
  • Heavy snowfall
  • High winds
  • Rapid increase in temperature
In the upper elevations (above 7000′), where a significant snowpack exists, deeper instabilities have generally been neutralized by warm temperatures and rain followed by a stabilizing re-freeze. The danger for persistent slab instabilities deeper in the snowpack is currently low.
Light snow is forecast for the next week with potentially strong wind. This will likely increase the avalanche hazard.
Early season conditions exist throughout the forecast area: rocks, stumps, and fallen trees increase the consequences for trauma if caught in an avalanche.
Careful terrain management and snowpack assessment is essential for safe backcountry travel.
If you get out into the backcountry, please share your observations on our public observation page.
Ski and ride safe.
The post Avalanche Special Update – Early Season Update – November 26, 2019 appeared first on Missoula Avalanche.
This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide to help you make more informed decisions regarding travel in avalanche terrain for the next few days.

Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to Hoodoo Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information for the Lookout Pass/St. Regis Basin is available from the Idaho Panhandle Avalanche Center.
 

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Avalanche Special Update – Early Season Update – December 3, 2019

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This is Travis Craft with an early season snowpack update, on December 03, 2019.
Variable snow and avalanche conditions exist throughout the forecast area. In general, a rideable base does not exist below ~6500.’
Most terrain above this does not have enough snow to produce avalanches, except in isolated areas. Remember, if there is enough snow to ride, there is enough snow to slide. Avoid terrain traps and wind loaded areas.
The most significant objective hazard that currently exists is thin snowpack coverage that could result in injury and/or gear damage. There are a lot of snags hidden just beneath the snow surface, which make for risky descent conditions. Keep this mind, and don’t let your season end before it really starts!
The region’s snowpack has poor structure but generally lacks large enough slabs to be problematic. Where a sizable slab exists on top of buried facets and crusts, stability tests have shown that there is very easy failure and propagation (observations).
Persistent slabs are the primary avalanche concern. On upper elevation (7000’+) terrain steeper than 35º, D1-D2 human triggered are possible. These are most likely where a consolidated slab overlies faceted snow and crusts. There may not be red flags or clues of this problem. Dig a snowpit, assess layers, and conduct a stability test.
Isolated upper elevation (7000’+) D1-D2 human triggered wind slabs are the secondary avalanche concern on leeward terrain steeper than 35º (especially if convex or unsupported). Be on the lookout for wind loaded terrain. Pole probing and hand pits are an effective means of efficiently assessing the wind slab problem as you travel.
Please send us your observations! Your findings help us produce a more accurate forecast.
Unsettled weather with relatively warm temperatures, mountain snow showers, and moderate to strong upper elevation wind is forecast. No significant precipitation is expected. However, any new snow and wind may increase avalanche danger.
We will do our next snowpack update on Friday, December 05, 2019.
Ski and ride safe.
The post Avalanche Special Update – Early Season Update – December 3, 2019 appeared first on Missoula Avalanche.
This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide to help you make more informed decisions regarding travel in avalanche terrain for the next few days.

Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to Hoodoo Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information for the Lookout Pass/St. Regis Basin is available from the Idaho Panhandle Avalanche Center.
 

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Avalanche Special Update – Early Season Snowpack Update – December 6, 2019

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December 06, 2019 Snowpack and Avalanche Update

A significant weather event is forecast this weekend for the West Central Montana backcountry. A substantial amount of new snow (favoring the Swans, Missions, and Rattlesnake) and wind are expected. Avalanche danger will increase.

Since our last update, we have experienced warmer temperatures and a few to several inches of new snow in the upper elevations (more in the northern advisory area). While temps will remain relatively warm into Saturday, they’re expected to drop with snowline falling to valley levels by Sunday.

There is a widespread persistent slab avalanche problem in the upper elevations, where a very poor snowpack structure exists across the advisory area. A slab is building on top of very weak facets that developed above the melt-freeze crust from the November 17 warm storm.

This snowpack structure lacks the strength to support significant loading from new snow and wind. Specific upper elevation areas, where the snowpack is deeper, are prone to human-triggered and/or natural avalanches. More widespread upper elevation terrain will become prone to human triggered avalanches with additional loading from new snow and wind.

Wind slab and new snow (storm slab and loose snow) avalanche problems are expected to develop this weekend. Avalanche danger will increase as a result.

The other, very serious, objective hazard across the forecast area is thin snow coverage. Snags (rocks, stumps, deadfall) lurking at and just below the snow surface are widespread. As a result, descent conditions are risky for injury and/or gear damage. The consequences of getting caught in even a small avalanche are also increased: trauma is likely.

This weekend’s weather forecast is for snow and wind: over a foot is possible in the upper elevations (increasing avalanche danger). Winds are forecast from the west initially, switching to easterly mid storm. Wind transport could significantly increase the load on leeward slopes, and multiple aspects may be wind loaded.

Red flags like recent avalanches, collapsing (aka “whumping”), shooting cracks, and rapid wind loading are how the mountains will communicate avalanche danger to you this weekend. Heed their warning!

Please share your observations with us. They help us provide a better forecast product, whether simple and basic or technical and detailed.


Ski and ride safe!
We will issue our next update on Tuesday December 10, 2019.
The post Avalanche Special Update – Early Season Snowpack Update – December 6, 2019 appeared first on Missoula Avalanche.
This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide to help you make more informed decisions regarding travel in avalanche terrain for the next few days.

Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to Hoodoo Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information for the Lookout Pass/St. Regis Basin is available from the Idaho Panhandle Avalanche Center.
 

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Avalanche Special Update – Snowpack Update – December 10, 2019

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This is Jeff Carty one of your new forecasters with a snowpack update for December 10, 2019.
The storm we were hoping for failed to produce the significant amounts of snow forecast on Friday. Snow did fall though, up to 12” in the Swan with amounts decreasing as you move south through the advisory area. The southern Bitterroots received the least amount of snow with a few inches. The freezing level was around 6000’ during the storm. Low elevations <6500′ continue to have coverage too thin to ski without hitting trees, rocks, stumps, and ground, areas above 6500 require careful skiing due to hazards just below the surface.
Light snow is expected daily in the Swan for the next few days, with potential for snow throughout the forecast area late Wednesday. Winds gusting to 37mph are forecast out of the southwest.
While the existing snowpack was not loaded enough to tip the balance into an avalanche cycle, it did gain weight and depth. Very poor snowpack structure, continuing winds and new snow available for transport mean that the likelihood for avalanches continues to increase.
Persistent weak layers continue to be the primary concern. Throughout our forecast area, the snowpack consists primarily of facets and crusts. Surface hoar formed in the southern Bitterroot; there is depth hoar in the Rattlesnake, and facets everywhere. The slab above the bed surface has been slowly growing and consolidating. Stability tests are showing a propensity for propagation with medium strength down to 16” thick. While these areas are still isolated, a consolidated slab of this thickness poses a serious hazard if an avalanche were triggered.
Wind will continue to load lee slopes throughout the week and further stress the underlying snowpack. The new snow that has fallen is light density and easily transported, increasing the likelihood of wind slabs.
Watch for and pay attention to red flags like recent avalanches, collapsing (aka “whumping”), shooting cracks, and rapid wind loading.
Terrain management is key for safe backcountry travel. Avoid convexities, terrain traps, and overhead hazards. As slabs stiffen, they may pull back onto lower angle terrain if triggered. Be conservative.
Please share your observations with us. Any information you can provide helps us forecast better.
Ski and ride safe!
The post Avalanche Special Update – Snowpack Update – December 10, 2019 appeared first on Missoula Avalanche.
This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide to help you make more informed decisions regarding travel in avalanche terrain for the next few days.

Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to Hoodoo Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information for the Lookout Pass/St. Regis Basin is available from the Idaho Panhandle Avalanche Center.
 

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Avalanche Special Update – Snowpack Update – December 12, 2019

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This is Travis Craft with a snowpack update for December 12, 2019. We will start standard forecasts on Saturday, December 14, 2019.
The forecast area received 2-6 inches of snow overnight and this morning. Winds were strong to moderate over the last 24 hours.
New snow and winds increased the avalanche danger. Winds have loaded leeward slopes, creating sensitive wind slabs. The new snow is falling on a variety of old snow surfaces, and bonding takes time. The new loading is testing the poor snowpack structure.
The primary avalanche problem is wind slabs. Winds actively loaded leeward slopes yesterday in our observations.
The second avalanche concern is persistent slabs. As new snow and drifted snow increase, the buried weak layers become more sensitive and reactive to human triggers. Stability tests are showing propagation.
The third avalanche problem is new snow. It takes time for the snow to bond to the old snow surfaces. Look for loose dry sluffs. In areas that have higher accumulations of snow, look for storm slabs.
The way to mitigate all of these hazards is to stick to lower angle terrain less than 30 degrees that is sheltered from the wind. Look for red flags. Red flags are the snowpack’s way of giving clues to instabilities. Dig a snowpit to look for buried weak layers.
More snow and wind is forecasted through the weekend. This will increase the avalanche danger.See the forecast.
Please share your observations with us. Any information you can provide helps us forecast better.
Ski and ride safe!
The post Avalanche Special Update – Snowpack Update – December 12, 2019 appeared first on Missoula Avalanche.
This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can use the information we provide to help you make more informed decisions regarding travel in avalanche terrain for the next few days.

Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to Hoodoo Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information for the Lookout Pass/St. Regis Basin is available from the Idaho Panhandle Avalanche Center.
 

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Avalanche Advisory for December 14, 2019

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The avalanche danger for the West Central Montana backcountry is CONSIDERABLE on all aspects above 6500 feet. Fresh snow and wind have overloaded our snowpack, creating hazardous avalanche conditions. Careful route finding and snowpack evaluation are essential today.
Good morning, this is Todd Glew with the West Central Montana Avalanche Center avalanche advisory for December 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 are currently in the teens. Snowtel sites are reporting over an inch of SWE and 12+ inches of snow during the past 24 hours, with gusty ridge top winds out of the WNW.
The snowpack varies significantly throughout our forecast area. The central theme is that we have a complex snowpack with the potential for large dangerous avalanches breaking near the ground. We have been experiencing red flags such as cracking and collapsing during the past week. Snow tests have also been propagating, failing near the ground. Stay off of and away from terrain steeper than 30 degrees.
The primary avalanche concern is persistent slab avalanches on elevations above 6500 feet. We have the recipe for dangerous avalanches today, with strong snow overlying weak snow. The snowpack has poor structure and the possibility for large dangerous avalanches, breaking near the ground.
The secondary avalanche concern is wind slabs found on leeward slopes near ridge tops. Be on the lookout for pillowy features near ridge tops or cross-loaded features. Also keep an eye out for cornices, which are sensitive and can break back further than expected. If you trigger even a small wind slab or cornice, it has the potential to step down, triggering a larger persistent slab avalanche.
If you get out in the mountains, be on the lookout for red flags such as cracking or collapsing. Dig a snow pit and perform stability tests. Be on the lookout for changing conditions as you gain elevation. Areas prone to avalanches are where strong snow overlays weak snow. Avalanches are more likely the higher you get in elevation. Conservative route-finding and terrain choice are essential today!
Any information is essential for creating an avalanche forecast. Please submit your observations here.
Avalanche and Weather Outlook
Continued snow showers are forecast through Sunday evening, with close to a foot of snow possible. Temperatures are forecast to rise into the upper 20’s above 6000 feet during the day, with gusty ridge top winds out of the WNW.
Due to the complex structure of our snowpack, any new snow and wind can tip the scale and raise the avalanche danger.
The post Avalanche Advisory for December 14, 2019 appeared first on Missoula Avalanche.
 

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Avalanche Advisory for December 19, 2019

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The avalanche danger for the west central Montana backcountry is MODERATE. Evaluate snow and terrain carefully. It is possible to trigger a large avalanche on steep slopes with shallow snowpacks.
Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for December 19, 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 24 F in the region. In the Bitterroot, winds are 11 mph with gusts of 17 out of the SE. In the northern part of the advisory area, winds are 16 mph and gusting 24 mph out of the SSW. No new snow.
High pressure has dominated the forecast area over the last couple of days with strong winds. The snowpack is quite variable and complex. Snow depths in mid and upper elevations vary from 18 inches to 3 feet. We are still getting propagation in stability tests. We observed several natural slides that happened in our last storm cycle on North slopes that released on the 11/19 crust facet combination in the central Bitterroot. We found surface hoar development on shaded, sheltered aspects in the Rattlesnake and Lolo Pass. The surface hoar will be our next layer of concern once buried(see photo gallery).
The primary avalanche problem is persistent slabs. The weak snowpack can produce large avalanches if triggered. Avoid likely trigger points(shallow rocky points and steep rollovers).
The second avalanche problem is small stubborn wind slabs. Look for wind loaded terrain. These are slabs are stubborn but can be triggered and step down into the deeper weak layers in the snowpack. Look for shooting cracks from skis or machine to identify this problem..
Bottom line: The snowpack can produce large avalanches on the 11/19 crust facet combination. Possible trigger points exist in shallow mid-elevation snowpacks and higher elevation start zones. Be diligent in terrain selection and snowpack evaluation: avoid shallow rocky sections and steep rollovers. Dig a snow pit. Look for red flags.
Avalanche and Weather Outlook
The snowpack structure is poor. New snow and wind will increase the avalanche danger. The storm should enter our forecast area later today. See the forecast. Pay attention to red flags and shifts in the weather. I will post the next avalanche forecast on December 21, 2019.
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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Current West Central Montana Avalanche Advisory
Posted: Dec 21, 2019 06:42 am
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Missoula Avalanche
Avalanche Advisory for December 21, 2019

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The avalanche danger for the west central Montana backcountry is MODERATE. Evaluate snow and terrain carefully. It is possible to trigger a large avalanche on steep slopes with shallow snowpacks. It is possible to trigger a small wind slab on ridge tops today.
Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for December 21, 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 28 F to 33 F in the region. In the Bitterroot, winds are 18 mph with gusts of 34 out of the South. In the northern part of the advisory area, winds are 8 mph and gusting 222 mph out of the SE. Trace of new snow in the last 24 hours.
In the last two days, the forecast area received 3 new inches of snow and had strong winds primarily on ridge tops in the upper elevations above 6500 feet. The snowpack structure is weak. When stepping off skis, you are penetrating to the ground up to your waist. The snowpack varies in depth from 18 inches to 3 feet. In pit tests, we are still getting propagation. We saw active wind loading on slopes yesterday.
The primary avalanche problem is persistent slabs. The facet crust combinations are still reactive in pit tests. The recipe for an avalanche exists in our snowpack(a consolidated slab of snow over a weak layer with a bed surface). It is possible to trigger a large avalanche on this layer on slopes greater than 35 degrees at upper elevations >7000 feet. Avoid likely trigger points(shallow rocky points and steep rollovers).
The second avalanche concern is wind slabs. Over the last two days, winds have been strong and created small wind slabs. These slabs may be small but, if triggered, could step down to the deeper weak layers to create a much larger avalanche. Look for shooting cracks from skis or machines to identify this problem.
Bottom line: The recipe for a triggered human avalanche exists on steep slopes above 6500 feet. I do not trust the structure of the snowpack. Punching up to your waist is a sure sign of instability in our snowpack. Look for red flags. Dig a pit. Use caution and ride on more uniform slopes. Manage the persistent slab and wind slab avalanche problems by riding on sheltered lower angle terrain.
Avalanche and Weather Outlook
Above-average temperatures and strong winds today. On Sunday, a cold front drops temperatures down to season averages. See the forecast. Pay attention to red flags and shifts in the weather. The avalanche danger will stay the same. Todd Glew will post the next forecast on December 24, 2019.
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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Current West Central Montana Avalanche Advisory
Posted: Dec 24, 2019 06:43 am
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Avalanche Advisory for December 24, 2019

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The avalanche danger for the West Central Montana backcountry is MODERATE. It is possible to trigger large dangerous avalanches in steep terrain. It is also possible to trigger wind slab avalanches in exposed upper elevation terrain.
Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for December 24, 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 are currently 15-20 F. Winds are light out of the west. There are currently snow showers in favored locations. Overnight there was a trace to 3 inches of snow reported in some locations.
The nitty-gritty is that we have a thin snowpack throughout our forecast area. The kicker is that we have the potential for avalanches in areas with enough snow to ski or sled. We have a complex snowpack structure, with depths ranging from 1.5 to 3 feet above about 6500 feet in elevation. If you are wondering how deep the snow is? Step off your sled or skis, and there is a good chance you may sink to the ground.
The primary avalanche concern is persistent slab avalanches. These avalanches are especially dangerous given the consequences of getting caught and carried in an avalanche failing near the ground. What we have is stronger snow overlying weaker snow, showing the propensity to avalanche in snowpit results. On all aspects above 7000 feet, with a slope angle 35 degrees or greater, persistent slab avalanches are a concern. Snowpit results are showing signs of propagation, meaning avalanches are possible. Red flags such as cracking, collapsing, and natural avalanches have also been recently observed.
The secondary avalanche concern is wind slab avalanches. This problem is most pronounced near upper elevation ridge tops. Keep an eye out for bulbous pillowy features located on the leeward side of ridges. Wind slabs may be stubborn, but if you trigger one, it has the potential to step down and create a larger persistent slab avalanche.
Bottom line: We have the possibility for human triggered avalanches on steep slopes above about 7000 feet in elevation. We have a complex snowpack that does not inspire much confidence in regards to stability. Keep an eye out for red flags such as cracking and collapsing. Also, dig a snowpit, but don’t base your results just off one pit as we have a vast amount of spatial variability in our snow pack. Keep an eye out for steep thinner areas, as that would a more likely place to trigger an avalanche.

Avalanche and Weather Outlook
Mountain temperatures today are forecasted to be 20-34 F, with light winds out of the west. Snow showers are expected today with a trace to 2 inches in favored locations. Pay attention to any new changes today in regards to wind and snow. Avalanche danger will remain the same.
If you make it out into the mountains, any information is great appreciated. Send us your observations here.
Ski and ride safe.
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Current West Central Montana Avalanche Advisory
Posted: Dec 26, 2019 06:51 am
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Avalanche Advisory for December 26, 2019

moderate danger
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The avalanche danger for the West Central Montana backcountry is MODERATE. It is possible to trigger large dangerous avalanches in steep terrain.
Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for December 26, 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 are currently in the single digits to low teens, with light winds out of the WSW in most locations. Sky cover is partly cloudy with no precipitation.
Over the past week or so, we have not received much new snow, just a few inches in favored locations. Despite the lack of snow, there is still the chance to trigger avalanches on all aspects above 7000 feet in elevation and 35 degrees or steeper. Snow pit results are still showing signs for propagation, failing near the ground. We have about 1.5 to 3 feet of snow above 6500 feet in elevation. The snowpack structure is weak and stepping off your skis or sled will quickly show you the snow depth, as you will sink to the ground.
Our primary concern is persistent slab avalanches. This avalanche concern is prevalent on all aspects above 7000 feet in elevation and 35 degrees or steeper. This avalanche problem is buried close to the ground and would be catastrophic if you are caught and carried in an avalanche. The most likely place to trigger a persistent slab avalanche would be in thinner areas, primarily found near rock and cliff bands.
According to the Oxford dictionary, the definition of persistent is “continuing to exist or endure over a prolonged period.” This definition nails our primary avalanche concern on the head. We have a complex snowpack with a persistent slab avalanche problem that may exist for the foreseeable future. We have weak faceted snow, capped with a stronger slab of snow above it. The poor structure of our snowpack lends itself to the potential for dangerous slab avalanches, failing near the ground.
Bottom line: We have the possibility for human triggered persistent slab avalanches on steep slopes above about 7000 feet in elevation. Persistent slab avalanches are pesky because often times snow pit results and ski or sled tracks on a slope are not a good indicator of the stability of the slope. A good analogy is to imagine a lunch tray on the side of a mountain. People could be skiing the mountain all day, until the one unlucky person skis over the lunch tray, which is the trigger point, creating an avalanche. Remember this analogy as you get into the mountains today.
Avalanche and Weather Outlook
Mountain temperatures today are forecasted to be to 18-29 F, with wind chills below 0 F. Winds are out of the SW, blowing 5-20mph with gusts as high as 30mph. SW winds are expected to increase this evening, with up to 4 inches of snow falling tomorrow.
Any new snow will make the avalanche danger rise, especially if it is accompanied by wind. Pay attention to any new changes in regards to wind and snow. Watch out for red flags such as cracking, collapsing, recent avalanches, and wind loading.
If you make it out into the mountains, any information is greatly appreciated. Send us your observations here.
Ski and ride safe.
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Current West Central Montana Avalanche Advisory
Posted: Dec 28, 2019 06:57 am
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Missoula Avalanche
Avalanche Advisory for December 28, 2019

moderate danger
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The avalanche danger for the West Central Montana backcountry is MODERATE. It is possible to trigger large dangerous avalanches in steep terrain.
Good morning, this is Todd Glew with the West Central Montana Avalanche Center’s avalanche advisory for December 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
We are currently under partly cloudy skies with mountain temperatures in the teens and light winds out of the NW. Over the past 24 hours, we have received 1-6 inches of snow in favored locations and .1 to .3 inches of Snow Water Equivalent (SWE).
The recent snowstorm was a nice change from the lack of snow during the past couple of weeks. Throughout our forecast area, our total snow depth is 1.5 to 3 feet above 6500 feet in elevation. The snowpack is weak, and stepping off your skis or sled provides one with a quick trip to the ground. Another fun fact about our weak and complex snowpack is that dangerous avalanches breaking near the ground are possible.
The primary concern is persistent slab avalanches. Snow pit test results are still showing signs of propagation, confirming that the snowpack is unstable. Natural avalanches have also been observed. We have weak snow located about a foot off the ground with about 1 to 2 feet of stronger snow sitting on top of it. This structure lends itself to the potential for human triggered avalanches. Persistent slab avalanches are a concern above 7000 feet in elevation with a slope steepness of 35 degrees or greater. The most likely spot you could trigger this type of avalanche is in thin rocky areas or open slopes with a connected slab of snow. I do not trust my life with this snowpack.
The secondary concern is new snow avalanches. In favored locations, we have received up to 6 inches of very light density snow. This new snow has landed on a variety of slick old snow surfaces such as melt-freeze crusts, rime ice crusts, and surface hoar. Yesterday the snow was easily sluffing on slopes above 35 degrees. I would imagine that this would be the case today. Use small, inconsequential test slopes to see how the new snow is reacting. If you notice the new snow is easily sliding on the old snow, then there is the potential for the new snow to move fast and far down steep slopes. This type of avalanche has the potential to push you off your feet, taking you for a ride.
Bottom line: The snowpack structure is weak, and the chance of getting caught in a large dangerous avalanche is possible. Avoid likely areas to trigger an avalanche, such as thin rocky areas or connected slabs of snow. Avalanches are possible in terrain above 7000 feet in elevation and 35 degrees or steeper.
Avalanche and Weather Outlook
Today mostly clear skies and light winds out of the WSW with gusts up to 28mph are expected. Temperatures will be in the twenties with wind chill values below 0 F. Late this afternoon and evening, clouds are expected to build, followed by more snow with up to 6 inches of snow by tomorrow evening in favored locations. Expect the avalanche danger to rise with any new snow or wind. Pay attention to any new changes, and look out for red flags.
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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Current West Central Montana Avalanche Advisory
Posted: Dec 31, 2019 06:59 am
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Missoula Avalanche
Avalanche Advisory for December 30, 2019

moderate danger
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The avalanche danger for the west central Montana backcountry is MODERATE. However, as the forecast snow arrives, the hazard will rise quickly. It is currently possible to trigger avalanches in terrain steeper than 35º. With the addition of new snow, it will be likely to trigger avalanches in 30º terrain. Watch for updated ratings as the storm progresses.
Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for December 31, 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
Snow is on the way. Starting Monday night and intensifying throughout Tuesday, 2+ feet of dense snow is forecast to fall by Wednesday night. Some areas will receive freezing rain or rain to up to 6000 feet. The Bitterroot and Swan will receive the most snow. Strong westerly and southwesterly winds will accompany the storm, increasing the load on leeward slopes.
After a snowy Sunday that deposited 1-4 inches of snow to the area, we had clear skies and cold temps Sunday night. As a result, we have extensive surface hoar on all aspects in the forecast area. Compounding this is a crust under the new snow that sits on near-surface facets. What this means is that there are multiple low strength, low friction sliding surfaces for the new snow to land on.
The snowpack varies widely throughout the forecast area, from very shallow in the southern Bitterroot to near seasonal norms in the Swan. Depths vary widely from bowl to bowl and aspect to aspect. Today in the Rattlesnake, the size of the depth hoar on north aspects, under a 51-inch snowpack, was alarming, while some south aspects between 6000-7000 feet had as little a 1 foot of snow. All of it, regardless of depth, contains a combination of facets and crusts.
Despite the poor structure, we have not seen widespread avalanches, yet. As it gets loaded with new snow likelihood of avalanches will increase. The incoming snow will consolidate into a slab quickly due to its density. Dense and wet snow could quickly overload buried weak layers.
Storm slabs that slide on the surface hoar/new snow/crust/facet combo may step down to weak layers deep in the snowpack and trigger much larger slides.
Without any new snow, the possibility still exists to trigger avalanches. Upper elevation and wind-loaded areas contain deeper, denser snowpacks that could produce large hard slab avalanches. The weak structure cannot be trusted. Avoid steep slopes and obvious avalanche paths. Be aware of potential trigger points such as rock bands and shallow areas. Early season conditions increase the likelihood of trauma if caught in a slide.
Currently, our primary concern is persistent slab avalanches. As the storm develops, it will shift to storm slab avalanches.
If you make it out touring, please, share what you find on our public observations page.
Ski and ride safe.
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Current West Central Montana Avalanche Advisory
Posted: Jan 01, 2020 06:52 am
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Missoula Avalanche
Avalanche Warning for January 1, 2020

high danger
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An avalanche warning has been issued for the southern Mission, southern Swan, Rattlesnake, and southern and central Bitterroot mountains.The avalanche danger for the west central Montana backcountry is HIGH. Human triggered avalanches are certain. The avalanche hazard is increasing with continued snowfall. Travel in avalanche terrain is not recommended. Avalanches may run long distances and avoid runout zones.
Happy New Year, this is Jeff Carty with an avalanche warning for January 01, 2020.This avalanche warning is valid for 24 hours. The avalanche warning will either be extended or terminated at 0600 on January 02, 2020. 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 snow is here. What started lightly on Tuesday has intensified and is bringing considerable snowfall to the mountains creating dangerous avalanche conditions.
Up to 2.3″ of snow water equivalent (SWE) fell as up to 12″ of heavy snow last night, adding considerable stress to a weak snowpack. 1-3″ more SWE is expected by Thursday night, more than doubling the extra weight that has already been added to the snowpack. Strong westerly winds with extreme gusts are accompanying it, rapidly increasing the load on leeward slopes. Temperatures will increase Wednesday with rain possible above 6000 feet drastically increasing thaw instabilities.
Clear skies and cold temps Sunday night created extensive surface hoar on all aspects in the forecast area. Compounding this is a crust under the new snow that sits on near-surface facets. What this means is that there are multiple low strength, low friction sliding surfaces that the new snow is landing on.
The snowpack varies widely throughout the forecast area, from very shallow in the southern Bitterroot to near seasonal norms in the Swan. Depths are widely varied from bowl to bowl and aspect to aspect. Monday in the Rattlesnake, the size of the depth hoar on north aspects, under a 51-inch snowpack, was alarming, while some south aspects between 6000-7000 feet had as little a 1 foot of snow. All of it, regardless of depth, contains a combination of facets and crusts.
Despite the poor structure, we have not seen widespread avalanches, mainly due to a lack of slab and weight on top of it. As new snow accumulates, adding weight, the likelihood of avalanches rapidly increases. The incoming snow will consolidate into a slab quickly due to its density.
Storm slabs that slide on the surface hoar/new snow/crust/facet combo may step down to weak layers deep in the snowpack and trigger much larger slides.
High winds are creating slabs many feet thick in leeward and cross-loaded areas.
The weak structure of the underlying snowpack can not be trusted. Avoid all slopes over 30º and be very aware of overhead hazard. The surface hoar that the new snow is landing on can propagate long distances, and it may be possible to trigger avalanches from flat ground, above or below a slope. If deeper instabilities fail they may create very large slides. Early season conditions increase the likelihood of trauma if caught in a slide.
Our primary concern is storm slab avalanches. A very close second is persistent slab avalanches. Both may happen simultaneously.
Please, share any avalanche or condition observations on our public observations page.
Ski and ride safe.
 

Scott

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Current West Central Montana Avalanche Advisory
Posted: Jan 02, 2020 06:56 am
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Missoula Avalanche
Avalanche Warning for January 2, 2020

high danger
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An avalanche warning continues for the southern Mission, southern Swan, Rattlesnake, and southern and central Bitterroot mountains. Our deepest condolences go out to the friends and family of two people killed in an avalanche in the Seeley Lake Region of our forecast area yesterday. We will provide more details later today or tomorrow. The avalanche danger for the west central Montana backcountry is HIGH. Human triggered avalanches are certain. The avalanche hazard is increasing with continued snowfall. Travel in avalanche terrain is not recommended. Avalanches may run long distances and avoid runout zones.
This is Todd Glew with an avalanche warning for January 02, 2020. This avalanche warning is valid for 24 hours. The avalanche warning will either be extended or terminated at 0630 on January 03, 2020. 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 are currently in the 20’s with gusty ridge top winds out of the W. It is currently snowing and blowing at many locations throughout our forecast area.
What a blockbuster of a storm, this storm just overloaded our weak snowpack with a significant amount of water weight. To help you better understand our primary avalanche concern, imagine trying to park a Mack Truck on top of a box of champagne glasses. The new storm snow being the Mack Truck, and the old snow being the box of champagne glasses. A recipe for disaster.
Our primary avalanche concern is persistent slab avalanches. We have multiple weak layers in our snowpack that have been overloaded by 1.5-3.5 inches of SWE in the past 48 hours. The SWE amount translates to 1.5 to 2.5 feet of new snow, sitting on top of an avalanche prone snowpack. Our first layer of concern is a surface hoar, crust, near-surface facet layer buried below the new snow. This layer has been failing in natural and human triggered avalanches. About a foot or so off the ground is another layer of concern, weak sugary depth hoar that has also been failing in natural and human triggered avalanches.
Our secondary concern is wind slab avalanches. Winds have been strong out of the W throughout this storm, forming wind slabs near ridges or on cross-loaded features. These can be identified by looking for bulbous or pillowy like features located on the leeward side of ridges. Remember, even a small wind slab has the potential to step down and create larger avalanches.
Bottom line: Avoid traveling in or below avalanche terrain today. Stay off of and far away from any slopes approaching 30 degrees in steepness. We have a dangerous snowpack that is screaming for us to stay away. Watch out for red flags such as cracking, collapsing, wind loading, and recent avalanches. There is plenty of fun to be had on low angle slopes out of avalanche terrain.
Avalanche and Weather Outlook
Today snow showers are expected throughout the day with additional accumulations of 2-6 inches possible. Winds will be strong out of the W with gusts up to 60mph expected. Temperatures will be in the 20’s today with wind chill values below 0. More snow is expected later this evening with another blast of snow this weekend. Stay tuned.
If you make it out into the mountains, any information is greatly appreciated. Please send us your observations here.
Ski and ride safe.
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Scott

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Current West Central Montana Avalanche Advisory
Posted: Jan 03, 2020 06:50 am
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Missoula Avalanche
Avalanche Advisory for January 3, 2020

high danger
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The avalanche danger for the west central Montana backcountry is HIGH In wind loaded terrain and CONSIDERABLE elsewhere. Dangerous avalanche conditions exist and travel in avalanche terrain is not recommended. Hazard may increase with high winds and rising temperatures, check for updates tomorrow.
Good morning, this is Jeff Carty with the West Central Montana Avalanche Center’s avalanche advisory for January 3, 2020. 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.
The new year came in with a bang. The storm has delivered up to 4.3″ of Snow Water Equivalent (SWE). More than 2 feet of snow fell in the Bitterroots, the southern Missions, and the Swan. The Rattlesnake received just slightly less. Winds gusted to 50mph and have averaged 35mph over the last three nights transporting considerable snow. Warm, near-freezing temperatures accompanied the storm, and much of the snow was dense as a result.
The storm has put tremendous stress on a snowpack with a very poor structure. In addition to the avalanche that resulted in the fatalities, multiple natural avalanches occurred throughout the forecast area. At least one of these failed in the buried weak layers near to the ground. A slide was remotely triggered at Lolo Pass. Widespread whumphing and cracking have been experienced throughout the forecast area. It has been difficult to assess the full extent of natural avalanching. Visibility has been poor; snow accumulation has been rapid, covering signs and travel has been hazardous. The avalanche cycle is likely more widespread than we are aware of and not yet finished.
Persistent slab is again our primary concern, the Dec. 29th surface hoar adding another persistent weak layer. It is widespread under the new snow throughout the forecast area and present at all elevations above 5000′. The nature of this layer means that avalanches can be remotely triggered from above, below, or adjacent to avalanche slopes from low angle terrain. It is very likely to trigger a slab on this layer, and it may step down to deeper persistent weak layers creating a much larger avalanche.
Wind slab is our other problem. I hesitate to call it a secondary concern as it is very touchy, present on all leeward and cross-loaded slopes, and certain to be triggered by the weight of a person or snowmobile. This wind slab may be several feet thick, and small slides may produce considerable debris capable of deeply burying people. Wind slab avalanches are likely to trigger persistent slabs.
Today temperatures are expected to rise above freezing throughout the forecast area at most elevations and stay elevated overnight. This will create thaw instabilities that may increase avalanche hazard by weakening bonds in the snowpack. Strong southwest winds with gusts to 50mph will continue to load slopes and build wind slabs. Minimal new snow, up to one inch is expected today.
The bottom line:
There is lots of good riding on low angle slopes, and there will be more powder in the future. The outcome of an avalanche with our current problems is not worth the gamble.
Slopes that may not be perceived to be avalanche slopes may avalanche with our current snowpack. Because slopes lack obvious signs or haven’t been witnessed sliding does not mean they are safe. Slopes down to 30º could slide given the low friction and propagation likelihood of the problem layers.
Very careful and critical terrain assessment is required. Travel in avalanche terrain is not recommended. Give a wide margin if traveling below slopes and paths. Always travel with a beacon, shovel, and probe, and knowledgeable partners.
Please share any observations you have on our Public observations page.
Ski and ride safe
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Everyone who plans to ride in western Montana should view this thread right now.
 
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