Strong winds, heavy snow, and warming temperatures will likely create very dangerous and sensitive wind slabs and Natural avalanches in leeward terrain. Human-triggered avalanches 2-4 feet deep are very likely.
Travel in Avalanche terrain, or on slopes steeper than 30 degrees is not recommended. This heavy snow has the potential to overload the snowpack which has persistent weak layers in the middle and near the ground. Red flags like recent avalanches, cracking, and or whumping or hollow sounds in the snow are indicators of danger.
Winds out of the South are forecasted to gust to almost 40 MPH. Around 2 feet of warmer, and heavier snow is forecasted that will help the wind create natural avalanches in leeward terrain where the snow will form sensitive slabs. Watch for signs of drifting, and red flags like cracking in the surface and or sounds in the snowpack like whumphs.
We have been tracking faceted persistent weak layers (sugary or sandy snow that is hard to make snowballs from) near the ground and in the middle of the snowpack that formed in October and November while the snowpack was shallow and the temps were cold. Natural avalanches already happened on these layers in most places that were steeper than 30 degrees, but this poor structure has 5 out of 5 lemons or bad snowpack properties. It will take some time and feet of snow to make this problem go away.
Triggering these layers will become easier with more snow load over the weekend. Initiating a fracture while performing snowpack tests has been hard and in most places where we have done tests, they show some potential to propagate or spread a fracture through the block.
Today's forecast is sponsored by Mile High Powersports in McCall...Thank You for supporting the Payettte Avalanche Center!
Strong South wind and 1-2 feet of heavy, warmer snow Saturday and Sunday will form wind slabs in leeward terrain where the wind will deposit snow and form slabs anywhere from 2-4 feet deep.
With this storm, It is likely that natural avalanches will be the result, but be careful as the snow just may need you to trigger the avalanche. Traveling in the mountains will become difficult as the snowpack will likely become upside down, or have thicker, denser snow over the fluffy blower snow that resided on the top. The mountain snowpack has been getting deeper, but in many places, it is still shallow enough to hit rocks and logs and holds weak layers that can fail and produce an avalanche. These weak layers are not that far down from the surface which makes it more likely that you can trigger them. Near the ground, especially near rocks, the snow is weak and sugary. The middle of the snowpack has a weak layer of near surface facets and surface hoar that formed on the surface around November 10-20th during dry cold conditions. Under the lens, these weak snow crystals are barely showing signs of rounding or strengthening.
Choose simple, low-angle terrain to play on this weekend as the snowpack heals...These wind slabs that form this weekend will take a few days to stabilize, but the persistent weak layers in the snowpack are going to remain a threat for some time.
Check out recent observations on our observations page, or submit one of your own. Whether you are seeing instabilities or not, It helps us with being more accurate, and it helps others a lot also. Photos and details are great if you got them, but whatever you may be able to share would help the community and be appreciated...Thank You!
