Avalanche Forecast
Regions: Cascades - South West.
More snow will continue to keep the backcountry dangerous in the West-South zone Monday. The snow totals are growing deep and it may not matter what kind of avalanche you trigger. Any avalanche could be large enough to bury you. Stay off of open slopes greater than 35 degrees.
Discussion
Snow and Avalanche Discussion
We received a report of another skier triggered avalanche on East Peak Sunday. This is the second avalanche on that mountain in 2 days. Both were on SW-W aspects between 5800’ and 6200’ and occurred on more standard ascent routes. This highlights the unusual loading pattern of the recent east winds.
We want to call attention to the odd weather lately. It has been extremely cold for a long time. The snow is falling at very high snow-to-water ratios. This isn’t our normal Northwest pattern. In short: unusual weather often leads to unusual avalanches. Don’t get lulled to sleep an fall into normal travel habits. Keep your head on a swivel and watch the snow around you. If you see anything strange or surprising, that may be the snowpack telling you it’s ready to break.
Snowpack Discussion
New Regional Synopsis Coming Soon
Avalanche Problems
Storm Slabs
This next storm seems focused on the southern section of our forecast area. With the very cold temperatures, we could see quite a bit of snow. Even though most of this snow is light and fluffy, it may fall at amounts and rates that cause storm slab avalanches. Any avalanche, loose or slab, can entrain enough snow to bury and kill you. This is a good time to be very cautious and avoid open slopes greater than 35 degrees. Be particularly leery of areas where the wind has affected the snow. This may be hard to see. Look for simple signs like the snow blown out of the trees, subtle drifts, or variable snow heights of the easy to find crust. The wind may be all that is needed to build that slab.
In some locations,m there may be a layer of weak sugary facet just above a very pronounced crust. So far we haven’t heard of any avalanches on this layer, but that could change. If an avalanche occurs on these facets, it could be very large and destructive.
We want to draw particular attention to areas further south in the zone. Areas near the Columbia River, Mt Adams, and Mt St. Helens could receive substantial amounts of snow. These areas could develop very dangerous avalanche conditions Monday.
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1