Avalanche Forecast

Mostly sunny and warm weather is expected again on Friday. The avalanche danger will push the needle towards the higher end of Moderate danger on Friday. Get off steep slopes early in the day and be aware of the overhead hazard to minimize your exposure. 

Loose wet avalanches will become likely on any steeper slope due to warming Friday. Pay attention to the integrity of surface crusts formed overnight. Backcountry travel early in the day is recommended 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 Friday. 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.

Any wind slab deposits caused from the snow received Monday in combination with moderate westerly transport winds should have stabilized by Friday. 

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 Friday is not expected to be as extensive as during the warm weather last week which more closely followed a period of heavier snowfall and caused consolidation and some stabilizing. Hence the Moderate avalanche rating in all areas versus the Considerable rating forecast last week. You will need 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 Thursday or Friday during the warmest temperatures and lightest winds. After a stormy March, the snowpack has undergone significant settlement and multiple melt-freeze cycles over the last week.

A front moved across the Cascades early Monday morning, resulting in a period of mostly light to moderate precipitation, cooling and moderate westerly crest level winds. Precipitation transitioned from rain to snow as cooling occurred, forming a generally good bond to the old melt freeze crust. Showers at cooling temperatures occurred overnight Monday through Tuesday. NWAC stations along the west slopes received storm snow amounts ranging from 3-9 inches as of Tuesday. A convergence zone helped the Stevens Pass area Monday night, depositing about a foot of new snow by Tuesday morning.

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 and even 60s Thursday 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.  

A brief transition back to winter like weather was reported by Dallas Glass in the Paradise area on Monday 4/4. Dallas observed the new storm snow was scoured down to the melt-freeze crust on wind exposed, westerly facing slopes, while some leeward, easterly facing slopes, received as much as 6-12 inches of wind loaded new snow as of Monday afternoon. However, a good bond was reported to the old crust layer with evidence of rain near treeline. No signs of recent avalanches were noted with no evidence of new storm slab development.

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 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.