Avalanche Forecast

Warming temperatures and rain will cause very dangerous avalanche conditions Monday. Avoid all avalanche terrain including in the runouts of large avalanche paths. Avalanches may originate at higher elevation bands and travel down to your location. Avoid areas with avalanche terrain overhead. Use a large safety margin of terrain between yourself and any avalanche paths. Avalanches may run over common travel routes. This is time to dial it back and be extremely conservative with your terrain travel at all elevations.

Wet avalanches could be very large and destructive on Monday. They can occur naturally and you can easily trigger them on slopes over 30 degrees. With limited visibility and observations in the past 24 hours there is a lot of uncertainty about exactly when and where wet avalanches will occur. Wet Slab avalanches are extremely difficult to predict and manage.

Some backcountry terrain, like slopes near Crystal Mountain, harbor a shallow and more layered snowpack. While these areas may not see as much rain, they will need less of it to produce Wet Slab avalanches.

Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended. Very large, wet avalanches are likely. All but the highest slopes have seen some rain in the past 24 hours. Conditions are primed for a major avalanche cycle. You can now trigger very large and destructive avalanches in terrain over 30 degrees.

Significant snow has accumulated across the west slopes over the last week and a half. Up to 4 feet of settled snow sits atop a crust formed in mid-January. Observers have reported many natural and triggered slab avalanches in the recent snow from a variety of aspects and elevations.

Warm temperatures and rain over the weekend created wet, heavy snow sitting over weaker storm snow. Near and above treeline winds have drifted snow into thick slabs on a variety of aspects. In many locations winds have deposited snow to twice the depth of sheltered areas.

Poor visibility and frequent storms have limited observations near and above treeline.

Observations

Central

On Sunday, an avalanche forecaster on Snoqualmie Pass reported wet loose avalanches in steep, rocky terrain below treeline. Other reports including rain in the morning, runnels forming in the snow below treeline, and water draining through the recent snow.

Also on Sunday an observer on Snoqualmie pass reported tests results at 3,000ft indicating propagation on a melt-freeze crust about 2 feet below the surface. This crust may be harder to find at higher elevations.

Observers reported a very large avalanche was reported on Friday from Chair Peak near Snoqualmie Pass.

South

NPS Rangers reported a very large natural slab avalanche on Sunday from an east aspect at 6,800ft in Van Trump Park on Mt Rainier. This released in recently wind drifted snow.

NWAC staff in the backcountry adjacent to Crystal Mountain observed wind drifting snow into stiff slabs on lee slopes near treeline on Friday. In sheltered areas, 2-3 feet of storm snow sat over the January 16th crust. Some south and west aspects in the area are very shallow with less than 5 feet of snow and more defined layers than most locations in the region.