Avalanche Forecast
Regions: Snoqualmie Pass.
The very cold storm pattern continues Monday. At this point, we have quite a bit of snow on the ground with several weak layers. All we need now is a slab. This is a time to be cautious, and avoid any open slope greater than 35 degrees.
Discussion
Snow and Avalanche Discussion
We did not see any new avalanches on Sunday around Snoqualmie Pass. There was evidence of a few small loose dry and storm slabs from Saturday that likely failed during the heaviest precipitation.
So far, this recent snow is very light and unconsolidated. We expect more of that on Monday. This is a classic incremental loading pattern. We just keep adding more and more weight to the snowpack. When will it break? That’s very tough to say. It could be Monday, only time will tell.
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
The missing piece from the avalanche equation lately has been the slab. We’ve had plenty of snow, but it’s just been too light and dry. That could change on Monday. This is a good day to play it safe and stay off of open slopes greater than 35 degrees. The snow totals are growing very deep, and we have seen subtle weak layers in the new snow. Whether you trigger a storm slab or a loose dry may not matter, there is plenty of snow to entrain and allow the avalanche to grow large and bury you. 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.
We have observations, in a variety of location, of a layer of weak sugary facets near the base of the recent snow. So far, we have not heard of any avalanches on this layer. On Monday, that layer could be 2 feet or more below the snow surface. Keep an eye out for sudden collapses, whumphs, or surprisingly deep avalanches.
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