Avalanche Forecast

Light showers should diminish overnight through Friday morning.  A low pressure system should glance the southern Washington Cascades with only light snow Friday afternoon while partly to mostly sunny skies should be seen further north.  

Due to recent observations received Wednesday and Thursday, persistent slabs are still possible to trigger in the CE zone, although there is still a fair amount of uncertainty regarding how spatially extensive this problem remains. Look for obvious clues like whumpfing or shooting cracks as evidence that persistent slab potential exists. Give this deadly avalanche problem the respect it deserves and continue to play it conservatively. 

Wind slab, potentially large, formed over the past few days on lee N through SE slopes will be the secondary avalanche problem near and above treeline. Lingering storm slabs problems should slowly diminish during the day.  

Use extra caution if traveling into the above treeline zone (alpine) as there have not been any recent observations from this elevation band. 

Snowfall over the east slopes the first week of December was about 1-4 feet. Then an atmospheric river arrived early in the week with additional snow in the northeast zone, rain in the southeast zone, with a transition in between in the central east zone. Almost 4 inches of water accumulated in 48 hours for Washington Pass and Holden ending early Thursday morning. 

Avalanche and Snowpack Observations 

We have varied conditions along the Cascade east slopes!  The forecast discussion is the same for the east slopes, but the danger ratings and problems differ by zone. 

A regionally deep snowpack exists in the northeast Cascades. Recent heavy precipitation along with a warming trend has likely thoroughly tested or buried persistent weak layers from earlier in the season. Avalanche problems are more likely to be storm related in the northeast zone. Persistent slabs now seem unlikely to trigger, but we will wait for more information before dropping this avalanche problem all together.  

NWAC observer Tom Curtis was at Blewett Pass in the central east zone on Wednesday and found sudden collapse test results in faceted snow at the November crust 15 cm from the ground.  On Thursday Tom found similar sudden collapses with buried surface hoar averaging 50 cm down at 5100 ft on the north side of Mt. Cashmere. More importantly Tom experienced whumpfing as this layer collasped and heard a natural avalanche release far from his observation location. We don't know how this layer fares as one moves further up in elevation, thus we'll forecast conservatively until more information is known about lingering PWLs in the central-east Cascades. 

The southeast zone should have a much shallower and stable snowpack affected by recent rain and warm temperatures. We have not received any observations from this zone.