L
Lambert454
Well-known member
Payette Avalanche Center
Forecaster: Dave Bingaman
Summary:
Today the avalanche hazard throughout the West Central area is going to remain Considerableon all Northwest through Northeast facing slopes over 35 degrees. The recent storms with their mixed precipitation and high winds that accompanied them have left a series of unstable conditions in the upper half of a fairly deep snowpack. We are seeing quite a few large natural releases throughout our forecast area and getting reports of avalanches that have been started directly and remotely by skiers on northerly slopes. This hazard is NOT going away anytime soon. The National Weather Service is calling for an additional 5-12 inches of snow through tomorrow with very high winds predicted to accompany this storm as well. Take the time to evaluate the terrain that you are playing in, and make sure that everyone in your party has the skills and proper equipment to be out in the backcountry right now.
Avalanche Concern #1: Persistent Slab
Yesterday we toured the West Mountain ridgline near Lone Tree, Poison Creek Drainage and into the Tamarack Falls area near Tamarack Resort. We saw evidence of several recent natural releases on northerly slopes. We also recieved reports of skier triggered slides from the Lick Creek area as well. All of these slides have a common theme. The weight of the new snow has overloaded the buried surface facet layers that we have been tracking for a good portion of the winter. The other common theme is that this layer is buried deep now, these slides are going at depths of 2.5-4 feet, this is not a small soft slab, it is a monster with big teeth. The potential for widescale propagation is very high with this layer as well when triggered. It is extremely important to consider what the slope that you are on is connected to. The slides that we have seen this week begining with the naturals that we saw in Lick Creek, the tragic slide near Hard Creek and the reports that keep coming
in all are demonstrating good propagation to adjacent slopes, across complex terrrain features and even into lower angle slopes. Our stability tests yesterday prove the propagation potential, we saw moderate results on our compression tests(CT scores in the 13-17 range) but extremely easy full block failures using the Propagation Saw Test(cuts of less than 1/3 of the block on 34-37degree slopes). The moderate CT scores only tell me that the this layer is now deep enough that our stability tests are not completely accurate at judging the amount of force needed to cause a failure but when triggered it goes big. This layer will continue to be a concern until we lose our snow this year. If you are out anytime between now and our thawout keep in mind that the northside snowpack could have a lingering instability until the bitter end. Check out the accompanying photos to see how deep the layer of concern is buried in the snowpack. The first photo shows the rain layer from this
week and the buried surface facet layers that are our biggest concerns, the second image is of an isolated block of snow at the beginning of one of our PST tests(note how deep the saw cut is).
Avalanche Concern #2: Storm Snow
We have another strong storm system entering our area today. Snowfall predictions are for anywhere between 8 and 12 inches of snow to fall today and tonight. High winds are also expected to accompany this system. Southerly winds are expected to be moderate this morning and reaching speeds up to 26MPH by mid day with gusts over 40 possible. The winds are expected to remain strong and gusty throughout the night tonight with a shift to the west and northwest. Watch for windslab formation on ridges with significant loading on North, Northeast and Easterly slopes. Brittle windslabs should be expected at or near ridgetops with a south, west or northwest exposure. With the additional snowfall and windloading in the next few days, we could see slides going MUCH deeper than we usually see in this area. Bottom line: more snow plus high winds...good possibility for more natural activity on loaded slopes with a very good possibility of human caused activity in these areas on
steeper slopes.
Recent Avalanche Activity:
Numerous reports of natural activity on northerly slopes and human caused slides on terrain over 35 degrees.
Mountain Weather:
Another strong system is entering our area today. Temperatures are expected to remain wintry with highs in the low 30s and overnight temperatures dipping into the teens. We have an 80-90 percent chance of receiving 8-12 inches by tomorrow morning with winds gusting into the 40's at our ridgetops. The extended forecast shows temps staying below normal for the next few days and another storm combining with a southwest flow of moisture approaching our area on Sunday night. Don't put your skis away yet, winter is definitely not over in the West Central area yet!
Announcements: Tomorrow will be our last regular forecast, we will be issuing backcountry updates periodically as conditions change. Please continue to send us your observation if you are out in the backcountry. Thanks to everyone that contributed observations this year.
This advisory provided by the Payette National Forest Avalanche Center. In partnership with the Boise and Payette National Forests, Idaho department of Parks and Recreation,Friends of the PAC, and the Idaho snowmobile license plate program.
DISCLAIMER: Above is information on each factor affecting today’s danger rating. All factors must be considered to develop a backcountry travel plan that will reduce your risk.
Forecaster: Dave Bingaman
Summary:
Today the avalanche hazard throughout the West Central area is going to remain Considerableon all Northwest through Northeast facing slopes over 35 degrees. The recent storms with their mixed precipitation and high winds that accompanied them have left a series of unstable conditions in the upper half of a fairly deep snowpack. We are seeing quite a few large natural releases throughout our forecast area and getting reports of avalanches that have been started directly and remotely by skiers on northerly slopes. This hazard is NOT going away anytime soon. The National Weather Service is calling for an additional 5-12 inches of snow through tomorrow with very high winds predicted to accompany this storm as well. Take the time to evaluate the terrain that you are playing in, and make sure that everyone in your party has the skills and proper equipment to be out in the backcountry right now.
Avalanche Concern #1: Persistent Slab
Yesterday we toured the West Mountain ridgline near Lone Tree, Poison Creek Drainage and into the Tamarack Falls area near Tamarack Resort. We saw evidence of several recent natural releases on northerly slopes. We also recieved reports of skier triggered slides from the Lick Creek area as well. All of these slides have a common theme. The weight of the new snow has overloaded the buried surface facet layers that we have been tracking for a good portion of the winter. The other common theme is that this layer is buried deep now, these slides are going at depths of 2.5-4 feet, this is not a small soft slab, it is a monster with big teeth. The potential for widescale propagation is very high with this layer as well when triggered. It is extremely important to consider what the slope that you are on is connected to. The slides that we have seen this week begining with the naturals that we saw in Lick Creek, the tragic slide near Hard Creek and the reports that keep coming
in all are demonstrating good propagation to adjacent slopes, across complex terrrain features and even into lower angle slopes. Our stability tests yesterday prove the propagation potential, we saw moderate results on our compression tests(CT scores in the 13-17 range) but extremely easy full block failures using the Propagation Saw Test(cuts of less than 1/3 of the block on 34-37degree slopes). The moderate CT scores only tell me that the this layer is now deep enough that our stability tests are not completely accurate at judging the amount of force needed to cause a failure but when triggered it goes big. This layer will continue to be a concern until we lose our snow this year. If you are out anytime between now and our thawout keep in mind that the northside snowpack could have a lingering instability until the bitter end. Check out the accompanying photos to see how deep the layer of concern is buried in the snowpack. The first photo shows the rain layer from this
week and the buried surface facet layers that are our biggest concerns, the second image is of an isolated block of snow at the beginning of one of our PST tests(note how deep the saw cut is).
Avalanche Concern #2: Storm Snow
We have another strong storm system entering our area today. Snowfall predictions are for anywhere between 8 and 12 inches of snow to fall today and tonight. High winds are also expected to accompany this system. Southerly winds are expected to be moderate this morning and reaching speeds up to 26MPH by mid day with gusts over 40 possible. The winds are expected to remain strong and gusty throughout the night tonight with a shift to the west and northwest. Watch for windslab formation on ridges with significant loading on North, Northeast and Easterly slopes. Brittle windslabs should be expected at or near ridgetops with a south, west or northwest exposure. With the additional snowfall and windloading in the next few days, we could see slides going MUCH deeper than we usually see in this area. Bottom line: more snow plus high winds...good possibility for more natural activity on loaded slopes with a very good possibility of human caused activity in these areas on
steeper slopes.
Recent Avalanche Activity:
Numerous reports of natural activity on northerly slopes and human caused slides on terrain over 35 degrees.
Mountain Weather:
Another strong system is entering our area today. Temperatures are expected to remain wintry with highs in the low 30s and overnight temperatures dipping into the teens. We have an 80-90 percent chance of receiving 8-12 inches by tomorrow morning with winds gusting into the 40's at our ridgetops. The extended forecast shows temps staying below normal for the next few days and another storm combining with a southwest flow of moisture approaching our area on Sunday night. Don't put your skis away yet, winter is definitely not over in the West Central area yet!
Announcements: Tomorrow will be our last regular forecast, we will be issuing backcountry updates periodically as conditions change. Please continue to send us your observation if you are out in the backcountry. Thanks to everyone that contributed observations this year.
This advisory provided by the Payette National Forest Avalanche Center. In partnership with the Boise and Payette National Forests, Idaho department of Parks and Recreation,Friends of the PAC, and the Idaho snowmobile license plate program.
DISCLAIMER: Above is information on each factor affecting today’s danger rating. All factors must be considered to develop a backcountry travel plan that will reduce your risk.
