Avalanche Forecast

We just can't shake the Considerable rating near and above treeline in this storm pattern despite a favorable cooling trend Saturday and only light to locally moderate new loading expected. Lingering wind slab formed earlier in the week should be less of an issue, but once again persistent SE to SW transport winds will build new wind slab on lee slopes Friday night and Saturday. Watch for firmer wind transported snow and be aware of local loading patterns in your terrain. Shallow storm slabs may build late Friday night through Saturday morning.   

Cornices should be less sensitive on Saturday, but they are large so continue to give them a wide berth when travelling along ridgelines since they can break further back then expected. 

When the sun does break out Saturday, mid-March sunshine will rapidly increase the likelihood of loose wet avalanches on steeper solar aspects with the potential to entrain heavy wet snow at lower elevations. 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 significant 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 Cascade 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 1 ft 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. The last known human triggered avalanche on this layer was also in the Washington Pass area on March 2nd. 

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.