Avalanche Forecast

A very weak trough should move across the area on Saturday, with the main effect a slight cooling and introducing some clouds mainly in the Northwest Cascades. There is a slight chance of a few showers in the Northwest Cascades but any precipitation there would be brief and light. Sunnier conditions should be seen in the southwest Cascades, Mt Hood and east of the crest.

The avalanche danger should decrease a bit on Saturday due to some clouds and slightly cooler temperatures compared to the past few days of hot weather. But wet snow conditions should still prevail on Saturday and the regional focus will continue on possible loose wet avalanches, cornice failures and glide avalanches.

Loose wet avalanches should still be possible on Saturday. Melt-freeze crusts can quickly break down in spring sunshine. In areas that have received more recent snowfall, small loose wet avalanches have the potential to entrain deeper layers. Be aware of terrain traps where even a small loose wet avalanche could have unintended consequences. Plan to avoid steep solar slopes by late morning/mid-day to minimize the problem.

Many areas have massive cornices along ridge-lines so avoid slopes below these overhead hazards. Unlike the loose wet problem you will not get advance notice that a cornice is about to fail. Cornices can break much further back on ridges than expected and releases can be unpredictable during the spring.

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

In most areas previous wind slab will have become assimilated into the upper snowpack in the warm weather. The likelihood of triggering older wind slabs should be mostly over with and wind slab will not be listed as an avalanche problem. But continue to watch for isolated firm wind transported snow on previous, non-solar, lee slopes in the upper part of the above tree line.

Weather and Snowpack

A large upper ridge and warm air mass has been over the Northwest several days causing very warm weather. Friday was another day of light winds, sunny weather and the warmest temperatures by far so far this spring. Temperatures on Friday are well into the 50's and 60's F at many NWAC sites on both sides of the Cascade crest. This weather has been causing a spring avalanche cycle in most areas and has shifted concerns to heat related avalanche problems the past couple days.

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

A spotty layer of surface hoar was buried on about 3/12 mainly in the northeast Cascades with the terrain most suspect being N through E facing slopes. The last known human triggered avalanche on this layer was in the Washington Pass area on 3/19 and the persistent slab problem has been removed from the east slopes forecast moving forward. 

No avalanches have been seen for a long time on a persistent surface hoar layer buried February 27th in the Washington Pass area and to a lesser extent the central-east zone. Avalanches releasing on or down to this layer are unlikely.   

Recent Observations

NWAC pro-observer Tom Curtis was out in the Table Mountain area of Blewett Pass on Monday and found about 6 cm of new snow in wind sheltered areas with up to 20 cm on lee north through east aspects near treeline. No recent avalanche activity was noted in the Blewett Pass area.

Tom was on Wenatchee Ridge near Lake Wenatchee on Wednesday in the 2-4000 foot range and found many slopes melted out. On slopes still holding snow he found natural and easily triggered loose wet avalanches on all solar slopes in the top 15-20 cm of snow.

Tom was out yet again on Mt Lichtenberg near Stevens Pass on Thursday and found widespread large natural loose wet avalanches on nearly all solar aspects with easy to trigger loose wet avalanches on non-solar slopes.

A report on Turns All Year for the Chiwaukums described big rollerballs and big resulting debris piles on Thursday.