The Avalanche Danger is High today above 7000 ft. Human triggered slab avalanches 3-4 feet deep are likely, especially where the dense slab of snow overlying weaker layers below is thinner and more easily influenced by the weight of a skier or snowmobiler. Heavy Snow and winds over the next 24 hours will increase the stress on the snowpack and likely cause Natural Avalanches. Wind slab and storm slabs will be growing and will likely be reactive to the weight of a person. Avoid avalanche terrain, especially leeward slopes, and stay far away from slopes aproaching 30 degrees.
Temperatures have been on the trend of warming. 1- 2ft deep storm slabs in protected areas may be sensitive to the weight of a skier or rider. Steep protected areas should be avoided and will be suspect hiding places for sorm slabs to be waiting for your help in making them fail.
Skier triggered Sunday Jan 3 near Big Cr Summit.
Winds are forecasted out of the South and to reach into the teens and low twenty's which is prime slab development speeds. Be cautious especially near ridgelines. Pay attention to obvious clues as to which way the wind has blown the snow as local terrain can influence wind direction and even cross load a slope that may not be on your radar. Red flags like shooting cracks and whoomphing should turn you around in your tracks. Stay far back from the edge of Cornices as they are growing past the edges and may fail back further than you may think.
Skier triggered windslab near Big Cr Summit on Sunday Jan 3
Our snowpack has a couple of facet layers that we have been getting results on in our test pits. One is a rain crust ,about 50 cm or a foot and a half from the surface, that formed December 21st and has some weak facets under the crust. This weak layer is not that far down and is not strong...we will likely see it fail in a natural cycle early this week as heavy snow overloads it. Our other weak layer, in the middle of the snowpack (most steep slopes had a natural avalanche cycle on this 12/21), exists is a dry, loose layer of faceted snow that formed during the early December high pressure. The snow above these weak layers is getting harder. Hard slabs are much more tricky to predict and generally have much higher consequences if you do trigger them.
This layer is getting buried deeper, but it refuses to go away and continues to show the potential to propagate when the right amount of force or load is added in pit tests. Shallower istabilities have potential to step down and trigger this layer. The potential to trigger this type of slab increases where the slab is thinner especially in uneven rocky terrain or if you trigger a shallow avalanche in the weaker layers above.
On shady aspects and at higher elevations the crystals in this weak layer are more loose and angular. On solar aspects, this layer is preserved under melt/freeze and rain crusts making it even more tricky to predict how it will react to loading. In the lower elevations, the snowpack warmed, had more rain saturation and refroze which helped to strengthen this weak layer making it less of a concern.
Fisher Cr Saddle North of McCall on Saturday Dec 2nd Test Pit
New weak layers of surface hoar were buried in the last few days resulting in shallow, soft slab instabilities just below the new snow. Anyone that was out in the snow over the last couple days probably noticed an annoying rime (freezing mist) that formed a couple crusts on the snow surface, caking goggles and gear alike. This thin little rime, or "zipper" crust should disappear with new snow added above it but should also serve as a reminder that even subtle layers can affect snow stability.
The incoming storm cycle beginning today and continuing through early Tuesday should be enough to either overload the upper problems in the snowpack (think crush it and flush it) or add enough depth to the snowpack that the problem of the early December persistent weak layer will be even more diffictult and less likey to be triggered by the weight of a skier or snowmobiler.
Pay attention to changing conditions through the day and treat each slope with a degreee of suspicion, lower angle slopes are skiing and riding better right now and will offer you the widest margin of safety when it comes to shallow an
***Make sure you and all of your partners are riding or sliding with ALL of the essential avalanche equipment and are traveling cautiously. Enjoy lower angle options right now. This is the time to AVOID slopes steeper than 30 degrees. Its time to get out, have fun, get rad, but realize that coverage and stability should drive your decision making. As the slab over older weak layers gains strength, uncertanty as to its breaking point increases. The slab over our weak layer of faceted, early December snow is growing in strength with the slow, incremental loading of the last few storms but the problem below is not going away. Pit tests continue to show a potential for triggering and propagation on this layer. The addition of new weak layers in the upper portion of the snowpack creates a scenario where triggering a shallow slide could be the straw that overoads our weak snow camel's back allowing shallow avalanches to step down into the deeper layers below creating a large avalanche with the potential to spread out across a slope very quickly.
Thank you to everyone that has been sending in observations this year. These help the forecast team form a clearer picture across the forecast area. We will be updating our observation form to make your submissions even easier in the next week.
Also, resort and backcountry skiers leaving our ski areas need to be aware that areas outside of the ski area boundary are not patrolled, have no avalanche control work being done in them and if you are injured skiing or caught in an avalanche, the ski patrol has no obligation and may not have the resources to assist you. Backcountry rescues are subject to the direction of the Sheriff's department and Search and Rescue Teams. Rescue could be hours away, even close to the ski area. Self rescue is your best option and that means that everyone in your party should have the gear, understand the risk, and have the ability to provide an avalanche rescue and to perform basic life saving medical skills. The backcountry adjacent to resorts has of the highest concentrations of avalanche incidents and fatalities every winter no matter where you are. Thanks to the Friends of the Payette Avalanche Center and our local resorts, you will now see beacon checkers at our backcountry gates. This is a great reminder of the risks you face when you leave the ski area.
