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.

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 as avalanche problems along the west slopes due to less snow in the past 24 hours, 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. NWAC sites along the west slopes above the pass levels had 4-11 inches of late season snow for the 3 days ending Friday morning. But only about 0-4 inches of this snow was in the past 24 hours so this snow has had some time to consolidate and partly or mostly stabilize.

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. 

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

An observation from the NWAC observation page Wednesday 4/13 from the Mt. Baker area showed a natural loose wet avalanche involving the new storm snow and running well. 

DOT professionals in the Chinook Pass area reported small natural avalanches on Wednesday 4/13 involving the new storm snow. Below 5000 feet on solar aspects, the snowpack had not refrozen and loose wet avalanches could easily gouge down to deeper wet grains on steeper slopes. 

NWAC observer Dallas Glass was out on Thursday 4/14. Dallas was in the Skyline area of Stevens Pass area and found 10-15 cm of new snow well bonded to the 4/12 crust.  Dallas was able to ski trigger small loose wet avalanches on steep slopes on all aspects. 

NWAC observer Lee Lzazara was also out on Thursday 4/14 in the Bagley and Anderson Creek drainages in the Mt. Baker area and found 10-15 cm of new snow on the 4/12 crust. He found 10 cm of wind slab over 20 cm of lower density snow on lee N-E aspects near and above tree line but these layers were not reactive. Several loose wet small to large loose wet avalanches from 4/13 that packed a punch were seen on all steep aspects.

Although Alpental was closed Friday 4/15 a couple of folks from the pro-patrol were on the hill and reported 4-5 inches of storm snow on the upper mountain. Small natural loose wet avalanches were seen on most steep slopes but misty weather with low visibility.