Avalanche Forecast

Light snow should begin Sunday morning and increase in the afternoon and evening, heaviest near the Cascade crest.  A slow warming trend is expected along with the increase in precipitation Sunday afternoon and evening. 

Increasing SW alpine winds Sunday afternoon will begin to transport snow onto lee slopes at higher elevations. Approach lee slopes with caution above treeline on Sunday, watching for signs of active wind transport.  

Be cautious when travelling on slopes with an exposed slick surface crust due to fall hazard, mainly mid and lower elevations. 

Uncertainty still exists surrounding extent and sensitivity of the persistent weak layer in the Blewett Pass and Mission Ridge areas. The precipitation event Friday will not be enough to test this basal layer with significant weight. Evidence and observations on this weak layer can be difficult to come by. Be prepared to adjust your travel to respect this low likelihood/higher consequence problem.

Despite all this new snow, early season hazards still exist. Many creek beds have still not filled in for the winter.

Little new snow fell late Friday night through Saturday as temperatures cooled along the east slopes of the Cascades. Extensive freezing rain accumulated at mid and lower elevations along the east slopes of the Cascades as well as in the Stevens and Snoqualmie Pass areas Thursday night and Friday. This significant freezing rain event has likely destroyed or capped a variety of existing snow surface forms. The newly formed crust is limiting the current avalanche potential and formed over a relatively strong older snowpack. 

Recent mild weather, especially at higher elevations, has allowed for the strengthening of lingering wind slabs and upper snowpack weaknesses. Small isolated winds slabs have still been observed, however the extent of this problem continues to decrease.

Precipitation types above treeline during the Thursday/Friday storm cycle have been not been directly observed. Therefore, the upper elevation extent of the freezing rain crust is not well known at this time. There may have been a mix of rain or moist to wet snow in the upper elevations, and travelers should use caution and assess surface snow conditions carefully in higher terrain. 

Snowdepth decreases substantially the further east of the Cascade crest one travels. In many areas below treeline, there is not enough snow to present an avalanche danger. 

Observations

North

On Thursday, 3 mm surface hoar was noted in the Washington Pass area up to 5,400 ft.

Central

A public observation from Friday in the Mission Ridge backcountry noted a 1/4" thick freezing rain crust up to 5000' making for treacherous travel conditions. 

A NWAC forecaster was in the Diamond Head area of Blewett Pass on Tuesday. Basal facets (2-3mm) were found above 5000' on NW-N-E aspects. Large column tests showed this layer was reactive and likely to propagate. However, varied surface roughness combined with an overall shallow snowpack made for a low likelihood of finding the right terrain to support an avalanche. Just like the nearby Mission Ridge area, this layer will need to be watched moving forward. 

South

No recent observations