Avalanche Forecast

Clouds should spread over the Cascades from south to north on Friday as moisture rotates northward and a weak frontal band offshore approaches. Light precipitation should develop during the afternoon hours, specifically in the south Cascades. Snow levels should remain moderate Friday, rising along with daytime warming. 

All the travel advice associated with Considerable danger will be pertinent on Friday. Strong winds and the cross-loading of slopes Wednesday night and Thursday will require cautious route-finding and conservative terrain selection Friday. Wind slabs and cornices along ridges should be less sensitive Friday but still capable of producing large avalanches in specific areas near and above treeline.

The loose wet potential should be relegated to steeper slopes primarily below treeline Friday but will have the potential to entrain heavy wet snow. Avoid terrain traps where even a small yet heavy loose wet avalanche would have serious consequences. 

The persistent slab avalanche problem will only be listed in the northeast zone and is most likely to be found on non-solar aspects in the above and near treeline band and stretching into the upper portion of the below treeline band.  This interface is likely getting harder for a human to trigger but if triggered is capable of producing large avalanches. Be aware that at depths approaching the 1 m mark the extended column test becomes a less reliable indicator of propagation across a column. Deeper tests like the propagation saw test or deep tap test may help but layer identification and terrain selection are your best friends for managing a persistent slab danger.

Weather and Snowpack

During a period of fair weather in late February, widespread surface hoar formed in the northeast zone mainly surviving outside of steeper solar aspects and wind affected terrain. A weak front buried the surface hoar layer in the Washington Pass area about 2/27 and to a lesser extent the central-east zone.  

The nonstop active weather pattern continues to push a storm system through the PNW almost every day or two with fluctuating but generally moderate snow levels. The last storm impacted the area Wednesday through Thursday with a warming trend that peaked Wednesday night with the frontal passage in the early morning hours and also featured very strong winds seen throughout the range. Winds decreased Thursday afternoon. Generally 1 to 1.5 inches of water accumulated along the east slopes in the 24 hours ending 4 am Thursday with minimal shower activity in westerly flow during the day Thursday. Snow levels rose above 5000 feet in the Mission Ridge area Wednesday night but stayed lower closer to the Cascade crest and in the northeast Cascades.  About 6-16 inches of snow accumulated through Thursday morning with the higher tallies of over a foot seen at Holden, Washington Pass NWAC and Lyman Lake and Hart's Pass NRCS stations. 

We are no longer tracking any layers of concern formed earlier this winter in the mid or lower snowpack due to lack of recent activity and confirming field observations. 

Recent Observations

Strong winds on March 3rd caused widespread natural wind slab avalanches in the NE zone. While many were contained to the recent storm snow, one larger slide on a N-NE aspect at Windy Pass likely released down to the February 27th PWL. 

Mission Ridge pro-patrol reported a very active day of control on Thursday, March 10th with 1-4 foot slides produced during control work on lee slopes below ridges. Wind slabs were sensitive and ran far.  Widespread cornice growth was also noted along ridgelines.