Avalanche Forecast

A weak low pressure system should produce 6-18 inches of snow for the west slopes of the Cascades Wednesday afternoon and night, with the most snow likely for Paradise and White Pass. A subtle warming trend Wednesday night may produce a spike in avalanche activity overnight. 

However the main event will be the storm system forecast Thursday afternoon through Friday morning.  A low pressure system tracking north across Washington State will bring increasing precipitation first for the south and central Cascades Thursday afternoon and then to the north Cascades Thursday night. This will be accompanied by a warming trend most pronounced in the south and central Cascades and a shot of strong SW winds Thursday evening through Friday morning. Stevens and Snoqualmie Passes are expected to stay as snow during the daylight hours due to cool easterly flow, but White Pass may change to rain in the afternoon. 

All of these weather factors will stress the upper snowpack still struggling to settle and stabilize. The warming trend and increasing snowfall will increase the likelihood of new storm slab layers.

Deep wind slab should be watched for on all aspects but should be found mainly on NW to SE aspects due to recent SW to W winds. Watch for firmer wind transported snow on varied aspects especially in areas of complex terrain.

Loose wet avalanches will only be listed for the southwest Cascade zone including White Pass, Crystal and Paradise. Rainfall below 4500-5000 feet will likely cause loose wet avalanches on steeper slopes that may entrain a significant amount of recent snow. 

There is still higher than normal uncertainty due to the fewer than normal backcountry field reports and the recent heavy snowfall. Add all of these factors together and err on the side of caution by avoiding avalanche terrain on Thursday and by making sure that if you are in the backcountry you have exit routes that do not cross avalanche paths. 

Cornices won't be listed as an avalanche problem but avoid travel on ridges near where cornices may have formed and avoid steep slopes below cornices that may fail at any time.

There has been enough snow lately that snow immersion suffocation accidents are possible. Travel with a partner and keep them in sight at all times.

Weather and Snowpack 

The most recent warm, wet storm arrived on Valentines Day forming a strong rain crust, now buried several feet or more in most areas along the west slope Cascade zones. 

Strong southwest flow carried a strong front across the Northwest on Friday evening March 3rd. Along the Cascade west slopes this caused strong southwest alpine winds, heavy, moist, dense new snow above about 3-4000 ft and wet snow or rain below about 3-4000 ft. A region wide avalanche cycle was seen late Friday and in certain areas on Saturday. 

The first week or so of March has been remarkably snowy; NWAC stations along the Cascade west slopes have had about 3 to 8 ft of snow in the past 6 days with the most at Mt Baker! Ski and foot penetration is very deep - tree well and snow immersion suffocation (SIS) is a real hazard until all the new snow has time to settle out. 

Recent Observations

North

Widespread 1-2 ft storm slabs and larger, 3-5 foot wind slabs were seen in the backcountry near Mt Baker on Saturday. A close call occurred on Mt Herman when a large wind slab was triggered, and partially burying two and fully burying one in a separate party at the base of the slide path after completing a run. It was a fortunate outcome with no significant injuries.

On Wednesday morning, Mt. Baker pro-patrol saw mostly loose dry avalanches running within the new 8" they had picked up Tuesday night. These results represent the ski area's mitigated terrain only.  

Central

WSDOT, Alpental ski area and NWAC Pro-observers in the Snoqualmie Pass area reported signs of a widespread natural cycle that had occurred Tuesday afternoon and evening, with D1-1.5 storm slabs featured on all aspects. NWAC pro-observers Ian and Matt found storm layers beginning to settle and not indicating likely propagation in column tests. The March 3rd melt-freeze crust was thin and down 70-85 cm in the below treeline band. Matt observed shallow wind slab on NW-N aspects near treeline. Small loose dry avalanches ran fast on steep rollovers below treeline but didn't entrain much recent snow. 

Early Wednesday morning, WSDOT Stevens Pass easily released wind and storm slabs during control work involving Tuesday/Tuesday night's storm snow. 

South

NWAC observer Jeremy Allyn was in the Crystal Mountain backcountry Sunday and reported a favorable profile of the recent storm snow on N and W aspects. There was about 90 cm of snow on the Valentines crust. Hand and ski tests and test cornice drops did not give results and wind effects were minimal in this area.

Crystal pro-patrol experienced touchy avalanche conditions during Tuesday afternoon's increased snowfall and warming but only limited results during control work Wednesday morning. These results represent the ski area's mitigated terrain only.  

Here is a nice photo example of the cornice features, captured Sunday near Crown Point in the Crystal backcountry by our good friend Seth Waterfall. 

Sensitive cornice and wind slab on Crown Point near Crystal Mountain on Sunday 3/5. Photo: Seth Waterfall