Avalanche Forecast

Orographic showers in cool NW flow aloft Thursday night will wind down Friday morning followed by with partial clearing in the afternoon. Moderate W-NW transport winds will also ease off late Thursday night and Friday morning. The avalanche danger will vary along the west slopes based on recent snowfall and wind affects seen since late Wednesday night.      

Fresh wind slab will continue to be a primarily hazard on Friday near and above treeline. By avoiding obviously wind loaded slopes, you can enjoy some fine late season conditions. Firm wind transported snow and snowpack cracking can be good signs of wind slab layers.

We will flip which loose snow avalanche we identify as the primary problem with more sunshine expected Friday afternoon versus Thursday. Loose wet avalanches will be likely on steeper solar slopes by mid-day or afternoon. Loose dry avalanches should be small but likely on steeper non-solar slopes. Be aware of terrain traps where even a small loose avalanche could have unintended consequences in the wrong terrain.    

Human triggered storm slabs are possible as new snow becomes more cohesive with daytime warming on Friday. Watch for graupel layers received Thursday night to become potential bed surfaces for storm slabs. 

Recently formed cornices have grown large. If traveling along ridgelines, be aware that cornices break much further back than expected and you don't want to go for a ride with a chunk of cornice. Despite the cool weather, cornice releases can be unpredictable during the spring.

Although not listed as an avalanche problem, glide avalanches can release unexpectedly so avoid areas below steep unsupported slopes or rock faces. 

Weather and Snowpack

A low pressure system crossed the Northwest on Monday and Tuesday. NWAC stations along the west slopes accumulated a few inches above 4000 feet during this time. Light rain was seen on Wednesday in the below treeline band before a cold front swept through Wednesday night with moderate westerly transport winds continuing through Thursday for the south and central Washington Cascades.

Post-frontal snow accumulations varied based on elevation, with only a few inches below 4000 feet and 6-14 inches above. The most snow was received at Paradise and Mt. Baker NWAC stations through Thursday afternoon. New snow since Monday is generally well-bonded to a moist crust buried March 22nd.  

Frequent March storms have built large cornices along ridges in many areas.

The mid and lower snowpack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

Snoqualmie Pass avalanche professionals reported loose wet avalanches triggered by light rain running far on Wednesday in paths below treeline. Glide avalanches releasing to the ground off of rock surfaces were also reported near the same Snoqualmie Pass paths Thursday morning. NWAC professional observer Dallas Glass was in Kendall Peak area of Snoqualmie Pass Thursday, and found small but sensitive wind slabs near treeline. Dallas also found loose snow concerns transitioning to a shallow storm slab problem by mid-day with settlement and daytime warming.

The Mt. Baker pro-patrol reported only scattered and small soft storm slabs in area Thursday morning.  Stevens Pass pro-patrol reported strong west winds had redistributed the new snow, but that the new wind slab was stubborn and generally nonreactive to ski cuts. 

Powerful glide avalanches remain possible in isolated terrain features such as on steep slopes with smooth bed surfaces and especially where the slabs are unsupported from below. These avalanches are not predictable in the sense that they are not tied to short term warming or rain events. We want to highlight the low likelihood-high consequence of this sporadic but ongoing avalanche hazard during this wet winter.