Avalanche Forecast
Regions: Cascades - North East.
The avalanche danger will increase throughout the day. By Tuesday afternoon, you may be able to trigger small avalanches in the new snow at upper elevations. Check how well the new snow is bonded to old surfaces, and use caution on slopes steeper than 35 degrees if you find six inches or more of recent snow that slides easily.
Discussion
On Monday, observer, Mark Allen toured in the Rattlesnake and Robinson drainages and found a shallow and weaker snowpack compared to areas closer to Washington Pass. Snow depths ranged from about 4 feet at lower elevation to about 5 feet at mid-elevations. A notable layer of well-developed facets lies about 2 feet below the surface and is more prominent than further west in the zone.
While new snow accumulation is forecasted to be light on Tuesday, there is some uncertainty. Snow will add up throughout the day, but should only accumulate around 3 inches by dark. You may find deeper snow totals and drifts at higher elevations. Expect moderate snowfall with up to another 8" of accumulation Tuesday night. Expect an increase in avalanche danger after dark on Tuesday. You can see recent observations from Washington Pass here.
Snowpack Discussion
New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.
Avalanche Problems
Storm Slabs
These avalanches will grow throughout the day. New snow accumulations may be deep enough to pose a hazard at upper elevations by afternoon. New snow will fall on a variety of old snow surfaces, including a slick crust formed since the weekend. Dig just below the surface to check if the crust is frozen of still soft. Use small test slopes to check if the snow slides easily on the old surface. Watch for recent avalanches and cracks shooting through the snow. If you see these red flag warning signs, use caution on open start zones and slopes steeper than 35 degrees. Avoid terrain traps where a small avalanche could have serious consequences.
You may still be able to find interfaces from storms starting January 10th, now as deep as 5 feet below the snow surface. Avalanches on these layers are unlikely. However, uncertainty exists about the snowpack on slopes at the highest elevations and in remote parts of the zone.
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: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1