Avalanche Forecast

An upper ridge and warm air mass should continue to build over the US west coast on Saturday with offshore surface flow developing over the Northwest. A warm front may clip the Olympics with some light rain or snow and clip the north Cascades with some clouds with fair weather further south and east of the crest.

The amount of sun, heat and recent storm snow should be the main factors to consider on Saturday. More heat and more recent storm snow will generally mean more avalanche danger. The most caution will be needed in the northeast zone where there is more recent snow.

Loose wet avalanches should be possible Saturday on steeper slopes involving snow received during the week. Watch for wet snow deeper than your boot tops, especially on steep solar slopes during the late morning to afternoon hours. But with increasing strong solar input all aspects could be affected even if skies are cloudy. Avoid areas below steep gullies and run out zones.

The potential for cornice releases will increase through the weekend. 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 also avoid areas below steep unsupported slopes or rock faces showing glide cracks.

Storm and winds slabs will not be listed due to reports of good bonds of storm snow to the 4/12 crust, and fast stabilizing rates seen during spring storms. However, be aware of the potential for isolated slab avalanche layers involving the new snow mainly on non-solar aspects of very high terrain.

Weather and Snowpack

We've had two big warm-ups and spring shed cycles since the end of March. Over this time period the snowpack has undergone significant settlement with lower elevation snow beginning to fade away and with an overall transition to a spring snowpack.

A front crossed the Northwest Tuesday afternoon and night. Then a cool upper and surface low pressure system moved east along the Washington-Oregon border on Wednesday and Thursday. The NWAC site at Washington Pass and NRCS sites at Harts Pass and Lyman Lake indicate 4-10 inches of late season snow in the 24 hours ending Friday morning. NWAC sites further south along the east slopes had 4-5 inches the past couple days but very little if any in the 24 hours ending Friday morning. So the most caution will be needed in the northeast zone where there is more recent snow.

Storms in March continued to build unusually large cornices along many ridges. The potential for low probability/high consequence encounters, such as cornice failures and glide avalanches from steep unsupported slopes and smooth rock faces, should continue for awhile this spring. 

Recent Observations

A report was received via the NWAC observations page of a large avalanche running across closed SR 20 which was found on April 10th. This large avalanche may have been triggered by a natural cornice fall during the end of the warm spell and may have stepped down to older weak layers or interfaces from late winter.

Large avalanche across SR20 just east of Washington Pass. Photo taken 4/11.

Otherwise DOT avalanche professionals working at Washington Pass area during the week reported a quiet week regarding natural avalanche activity. Colder snow remained intact on non solar aspects around 6000 feet. Glide cracks and moats near rocks were reported as large for this time of year, likely due to the unusual warmth seen earlier this month.