Avalanche Forecast

A few isolated snow showers may linger Monday, while winds should be light and temperatures remain cool. 

This should allow for a slowly improving avalanche danger as recent storm and wind slabs begin settling and stabilizing. However, storm and wind slab conditions should remain sensitive or still likely to trigger in specific areas especially above treeline.

Heightened avalanche conditions are expected on specific terrain features, evaluate the terrain and snow carefully.

Travel conservatively by staying off, or avoiding steep wind loaded terrain.

Persistent slabs now seem unlikely to trigger, but we will wait for more information before removing this avalanche problem all together. Look for obvious clues to turn around like whumpfing or shooting cracks as evidence that persistent slab is an avalanche problem in the near and below treeline zones.  

Use extra caution if traveling into the above treeline zone 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. 

Since late Tuesday, 1-3 feet of new storm snow had accumulated in the NE Cascades near Washington and Harts Passes through Sunday afternoon. 

Avalanche and Snowpack Observations 

We have varied conditions along the Cascade east slopes!  Greater recent snow has accumulated in the NE zone. 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 the buried persistent weak layers from mid-November. Current avalanche problems are more likely to have shifted to storm related weaknesses in the northeast zone. Persistent slabs now seem unlikely to trigger, but we will wait for more confirmation before removing this avalanche problem all together.  

Reports from Delancy Ridge on Saturday up to about the near tree line elevation indicated storm snow was well bonded to the underlying recently formed crust from last week. No avalanches were reported with shallow wind slabs confined to isolated pockets. No observations were made above treeline where more widespread wind slab conditions were suspected. 

NWAC observer Tom Curtis was at Blewett Pass in the central east zone 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 collapsed 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.  Further east in this zone, Mission Ridge pro patrol did not find the recent storm snow particularly reactive during control work Friday morning, nor was there any evidence of lingering weak layers. 

Saturday, Tom Curtis and Ian Nicholson travelled to Jove Peak near Rainy Pass east of Stevens Pass. There was no evidence of the PWL in observations up to 5000 feet on S-W aspects. As of Saturday there was about 35 cm of storm snow over the crust.  

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