Avalanche Forecast

A frontal band of rain will progress across the Cascade West slopes on Wednesday night, with moderate to occasionally strong southerly winds during the evening hours. Precipitation has started as rain in most of our forecasting terrain. Light to moderate rain and snow showers on a moderate SW flow and a significant cooling trend follow the frontal passage during the late evening hours. Thursday will feature continued gradual cooling with the showery pattern initiated Wednesday night and light to moderate SW winds. 

Note that a refreezing 1/17 rain crust will form Wednesday night and provide a bed surface for wind and storm slab avalanches on Thursday.

Cascade West-North above treeline terrain will have dangerous wind slab and storm slab on Thursday. The upper elevations of the above treeline terrain in this zone will not see all snow with the Wednesday night storm system, adding far more new snow relative other locations during the peak intensity of the storm. During the period of strong southerly winds snow will be available for transport, creating dangerous and touchy wind slabs. Storm slabs will be touchy and deep on Thursday due to the high precipitation rates Wednesday evening with additional loading on Thursday. Travel in above treeline terrain is not recommended in this zone and larger paths on higher North Cascade peaks may produce very large natural avalanches so avoid large slide paths at lower elevations on Thursday.

In all other zones and at lower elevations rain provides a delay in the development of storm and wind slab problems. These areas are described below.

Wind slab is the most significant avalanche problem on Thursday. In the early morning hours the snow line lowers and winds will be moderate and shifting to the SW, transporting storm snow as it falls. Wind slabs will continue to load during the day Thursday as lower density snow will be easier for light to moderate winds to move. Wind slabs are most likely on NW-N-NE-E-SE aspects, but remember that complex terrain can move snow onto aspects you don't always anticipate. Wind slabs will be sensitive to human trigger and increasingly large at higher elevations on Thursday. Avoid wind-loaded slopes, particularly near and above treeline.

Storm slab will form in all elevation bands as the snow line lowers, but is most likely to form and become reactive in locations receiving higher snowfall rates that are favored in SW flow, such as Mt. Baker and to a lesser extent Mt. Rainier. Adjust your terrain selection in accordance with the new snow accumulation, becoming more conservative where 8 or more inches of fresh snow has fallen.

Lower snowfall amounts anticipated in the Cascade Passes will make storm slab less massive/reactive and wind slabs generally smaller, reducing danger relative to other areas.

Even a small small avalanche can have significant consequences in a bad location such as avalanche terrain exposed terrain traps or rock/tree hazards.

Remember that new snow will falling on a snowpack that has yet to gain full winter coverage, particularly at lower elevations. Terrain travel and access will still be a challenge in many some areas on Thursday and submerged obstacles will exist.

A trace to 2" of high density snow fell Wednesday morning on a warming trend as warm front lifted across the Cascades and should be well bonded to 2-4" of higher elevation snow that fell on Tuesday. These small amounts of recent snow should be melting and rounding from rainfall currently saturating the snowpack will into the above treeline terrain on Wednesday afternoon.

Recent snowfall sits on well-drained, generally saturated snowpack with less saturation in the above treeline terrain, but multiple crusts extending into this terrain. There are no notable layers of concern at this time. Thus, focus your attention on new storm instabilities in these zones moving forward.

Observations

North

On Wednesday afternoon, Mt. Baker Pro Patrol observed evidence of several large, natural loose wet avalanches visible on Shuksan arm at approximately 3000 ft. The avalanches are suspected to be from earlier Wednesday. 

Central

No recent observations

South

No recent observations