Avalanche Forecast

9 AM Update: Avalanche control performed mainly with explosives this morning are triggering large storm slab avalanches at Stevens Pass, Snoqualmie Pass and Mt. Baker. These slides are propagating easily and running well. In areas lacking a slab structure, initially small loose dry avalanches are entraining deeper snow layers. The danger has been raised to High near and above treeline with human triggered avalanches very likely on steeper slopes. 

Previous Discussion: More snow is on the way Saturday night and Sunday with a cooling trend forecast. W-SW transport winds should also decrease during the day.  

Despite a cooling trend, recently formed storm slabs should still be sensitive Sunday. While storm slabs are most likely to release within the most recent storm layers, various sun and rain crusts throughout the region are capable of providing bed surfaces for larger avalanches in isolated terrain.  If precipitation rates become more intense than predicted in the south Cascades Sunday, be prepared for the possibility for new storm slab instabilities. 

Colder temperatures will help preserve wind slab instabilities near and above treeline. We've highlighted more traditional lee easterly aspects on the elevation/aspect diagram, but be aware of cross-loaded slopes and that easterly winds earlier in the week loaded westerly aspects. Feel for firmer wind transported snow as you climb higher in the terrain. 

Enjoy the new snow but choose conservative terrain and allow storm related instabilities time to heal.  

Weather and Snowpack

Strong NE-E winds were seen this past Wednesday and Thursday with very cold temperatures. Fresh, touchy wind slabs formed with large plumes of snow visibly transporting loose snow from exposed terrain. 

A storm cycle began Friday with generally 1-2 feet of snow accumulating along the west slopes, with slightly lower totals at White Pass and a whopping 30 inches at Mt. Baker through 5 pm Saturday. A slow warming trend affected all areas Saturday with rain reaching 4000-4500 feet in the south Cascades. Easterly flow kept temperatures locally cooler at Pass level at Stevens and Snoqualmie Pass through the day. 

Recent Observations

North

Mt. Baker pro-patrol reported easily triggered storm slabs with ski cuts and explosives on all aspects averaging 12-18" and releasing within the new storm snow Saturday morning.  

Central

NWAC pro-observer Ian Nicholson was out on the lower slopes of Jim Hill east of Stevens Pass Saturday and found sensitive storm slab on short test slopes and in column tests averaging 20-30 cm down and failing within storm layers. 

Stevens Pass ski patrol reported widespread shallow storm and wind slab during morning control work. Alpental pro-patrol reported similar results mid-day Saturday with storm or soft wind slabs running well during control with ski cuts and explosives.  

NWAC received a report of a natural 6-12" storm slab, 150' wide, that released at 4300 ft on a SE aspect in the Kendall trees. Warming above the inversion was causing natural pinwheeling.  

NWAC pro-observer Jeremy Allyn was in the Alpental Valley Saturday and in the area he traveled below treeline found new storm snow generally lacking a cohesive slab structure with the new storm snow bonding well. Wind transported snow was not observed below treeline. 

South

Crystal mountain patrol reported sensitive but shallow wind slab on lee slopes below ridgelines Saturday. Pockets of sensitive storm slab could be found mid-slope up to 12" deep.