Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
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The Bottom Line: At upper elevations, avalanches may be deep and unsurvivable. Dangerous conditions exist after another significant storm has added more snow over a very weak layer. Stay off of, and out from underneath slopes steeper than 30 degrees if you see signs of danger like recent avalanches, and shooting cracks.
Snow and Avalanche Discussion
When digging around for information today, the most common response was "I thought about going out, but the snow quality seemed low." We are in the dark regarding what happened during the storm. We do know that we picked up anywhere from 0.3” to 1.2” of water equivalent, with the Salmon la Sac being the winner. Conditions are likely very dangerous in that area, and as one goes up in elevation.
Mission Ridge and Blewett Pass only picked up a few inches of new snow. A freezing rain crust formed up to about 4500ft across the eastern slopes, with a rain crust likely up to at least 6,000ft. Above 6,000ft the new snow is likely sitting on a recent crop of surface hoar and/or facets, which could make for poor bonding and potentially wide avalanches.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
