Avalanche Forecast

A frontal system will continue to bring significant snowfall to the west slopes of the Cascades Tuesday night, with moderate to occasionally strong crest-level winds and a slight warming trend. On Wednesday, rain and snow showers will be light to occasionally moderate along with lighter crest-level winds. 

Storm slabs developing in many areas Tuesday afternoon will build to 1-2' in many areas by Wednesday morning. Storm slabs will remain touchy Wednesday, with the potential to entrain the deeper lower density snow from the past week that exists in all areas, allowing these slabs to run farther and become larger than you expect. Stick to lower-angle terrain that is well-supported or heavily terrain anchored. 

Moderate to strong winds are transporting the new snow, particularly near and above treeline. These will continue to build touchy wind slabs near and above treeline on a variety of aspects. New or recent wind slabs may also produce large avalanches, entraining significant amounts of deeper loose dry snow. Avoid wind-loaded terrain and consider any aspect to be fair game for wind slabs on Wednesday.

Light to moderate rain will likely mix up to 4000 feet in the central Cascades (Stevens,Snoqualmie) and 4500 feet in the southwest Cascades (Paradise, Crystal, White Pass), creating the potential for small to large loose wet avalanches at lower elevations.  Small loose wet avalanches may become large and powerful if there is enough snow to gouge and entrain. Avoid steep terrain with exposure to terrain traps at lower elevations.  

The avalanche danger will lower slightly during the day on Wednesday, but the potential for triggering a large avalanche remains. Recent storm and wind slabs require time to heal, so be patient and match your terrain selection appropriately. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times.

Snow immersion and tree-well hazards will pose a very real danger on Wednesday. Maintain constant communication with your travel partners.

A snowy pattern that began 1/16 continues to bring new snow nearly every day to the west slopes of the Cascades. Since the rain event on 1/16, 3 to 4 feet of snow has fallen at NWAC stations from Snoqualmie Pass and north, with 6 feet at Mt. Baker. 1.5 to 3.5 feet of snow accumulated at stations in the Mt. Rainier and White Pass areas.

A storm on Tuesday is building touchy and generally shallow storm slabs in many locations within the 6-12" of higher density storm snow. E or SE winds were moving snow on Tuesday. Below the recent storm snow, the snowpack is generally right-side up with some lingering storm snow weaknesses. This upper snowpack is well-bonded to the 1/16 melt-freeze crust throughout the Cascade west slopes.

Moderate to strong winds transported snow forming wind slabs on a variety of aspects at Snoqualmie Pass and the southwest zone including Crystal, Paradise and White Pass on Sunday. Less wind transport occurred in the Stevens Pass area Sunday.  

Observations

Central

On Tuesday, NWAC avalanche forecasters  in the Skyline ridge area (near treeline and below) reported 3' of snow received during this storm cycle sitting above and well bonded to the 1/16 crust. Higher intensity snowfall began creating shallow storm slabs in the afternoon, with cracking observed generally in the new shallow snow, but occasionally breaking down to an older storm instability about 1' deep. East winds were transporting snow.  A professional in the Smithbrook area also reported increasing wind transported snow near treeline and one skier triggered soft slab avalanche on a south aspect near 5000'. 

On Tuesday, an avalanche professional in the Alpental Valley/Source Lake area observed slabs becoming reactive 10" down by early afternoon and still building. Moderate to strong winds were transporting new snow throughout the day. 

South

Professionals in the Crystal area Monday reported 1 to nearly 2 ft of snow above the 1/16 crust in wind sheltered terrain generally well bonded. In areas stripped of snow during Sunday's storm, less than 8" sits above the most recent crust and is poorly bonded. Loose dry avalanches were the biggest avalanche problem encountered Monday, found in steep terrain at higher elevations and easily ski triggered with the potential to run long distances.