Forecast rain overnight and temperatures above freezing on Wednesday mean that avalanches from melting snow remain possible on Wednesday. At elevations near treeline and in the alpine, cornices remain weak. Cornice collapses could trigger avalanches on weak layers deep in our snowpack. Wet loose avalanches will be possible below treeline, and likely in the lowest elevation ski terrain.
Cornices will remain particularly weak as long as warm and wet weather continues. Avoid traveling near cornices. They can break further back than people commonly expect. Cornice falls may provide enough force to trigger weak layers deep in our snowpack, and the resulting avalanche would be very large.
Deep Persistent Slab avalanches are unlikely, but a large Cornice collapse could trigger an avalanche on weak layers deep in our snowpack. These persistent weak layers were formed in late December and early January and are now buried over 2 meters deep. At this point my travel advice for managing this problem is to avoid traveling on large, steep slopes that have large cornices overhead.
Rain in the forecast for the early morning hours will keep Wet Loose avalanches on the problem list. After several days of warm temperatures and last week's rain any new Wet Loose avalanches will be relatively small. Wet Loose avalanches are most likely on very steep slopes below treeline and at pass elevations. Small test slopes can be a good tool for assessing the danger posed by Wet Loose avalanches, as is stepping out of your skis/board/sled and seeing how deep the slushy snow is.
After last weekend's rain and some very warm temperatures early this week, the mountains are steadily cooling off. We should be back to a more wintery temperature regime by the end of this week. As the temperature drops below freezing, instabilites from melting snow will resolve themselves. Following heavy snowfall mid-month, several periods of rain, and our most recent warm temperatures, I expect that when winter weather returns we can stop worrying about persisitent weak layers deep in the Cascade snowpack.
