Avalanche Forecast

A shift to onshore flow will maintain fair and mild conditions Sunday, but slightly cooler than the previous several days. Winds should remain light Sunday with some night and morning low level clouds possible in the valleys.  Freezing levels and temperatures should remain near 10,000 feet Sunday. Stay aware of the overhead hazard to minimize your exposure. 

Surface crusts should form overnight through the early morning hours followed by gradual melting and weakening. Pay attention to the integrity of surface crusts formed overnight. Loose wet avalanches will be possible on any steeper slope due to warming Sunday. Backcountry travel early in the day is encouraged since conditions can change rapidly due to daytime warming. Watch for wet snow deeper than your boot tops, especially on steep solar slopes during the late morning to afternoon hours.

The potential for cornice releases will continue on Sunday. Cornice releases can be unpredictable during the spring so avoid areas below cornices and remember that cornices can break much further back than expected along ridges.

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

Avalanche activity on Sunday should be less extensive as during the very warm weather last week which more closely followed a period of heavier snowfall and caused consolidation and some stabilizing. Continue to evaluate avalanche conditions on specific terrain features and change your plans if snow conditions are more dangerous than expected.

Weather and Snowpack

A large upper ridge dominated the weather last week through early Sunday, April 3rd, resulting in very warm and dry weather. A spring avalanche cycle occurred in most areas over this stretch, likely peaking a week ago, Thursday and Friday. After a stormy March, the snowpack has undergone significant settlement and multiple melt-freeze cycles over the last two weeks.

The last precipitation occurred early Monday morning with showers Tuesday, depositing storm snow from 3-12 inches, now indistinguishable following several melt freeze cycles during the very warm weather. 

Another upper ridge is currently over the Northwest, causing sunny weather and warm temperatures. High temperatures at many NWAC stations throughout the Cascades pushed into 50s, 60s on Thursday with even a few 70s recorded Friday afternoon!  

Frequent March storms have built unusually large cornices along many ridges.

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

Numerous professional and recreational observations focused on the spring avalanche cycle that occurred last week throughout the west slopes of the Cascades.  

NWAC observer Lee Lazzara was in the Mt Baker backcountry Tuesday 4/5 and reported about 4 inches of storm snow, well bonded to the moist old melt-freeze layer. There were some specific features that had up to a foot of wind loaded snow, but good bonding and settlement kept that snow from moving. He was out again in the Swamp Creek drainage on Wednesday 4/6 and found similar conditions. Debris from a large heat related avalanche was seen from a steep, complex northwest facing slope. The main take away currently in this area is to continue to be aware of the potential for low probability/high consequence encounters, such as cornice failures and glide avalanches from steep unsupported slopes and smooth rock faces.

On Thursday 4/7, WSDOT avalanche professionals in the Chinook Pass area reported a natural loose wet cycle occurring in the early afternoon on solar aspects. Most loose wet avalanches were small and not entraining much surface snow but were widespread.  

Crystal mountain pro-patrol on Friday, 4/8 saw little in the way of loose wet activity, but reported isolated cornice failures triggering wet slab avalanches of about 2-3 ft deep and 50' - 75' wide.   

Dallas Glass was in the Stevens Pass backcountry Friday, 4/8 and found a supportable melt-freeze crust breaking down by late morning on the east through south aspects. Most natural loose wet activity was small and confined to steep slopes below rock bands. Debris from one larger loose wet avalanche was observed on an east aspect around 5500' that likely occurred Thursday afternoon.