Avalanche Forecast

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.  

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. 

Despite a cooling trend, recently formed storm slabs may still be sensitive Sunday. While storm slabs are most likely to release within the most recent storm layers, sun crusts on solar aspects may be more sensitive to triggering. If precipitation rates become more intense than predicted in the southeast and central-east Cascades Sunday, be prepared for the possibility for new storm slab instabilities. 

Natural or human triggered small loose dry avalanches are possible in steeper terrain. Avoid terrain traps where a small but fast running small loose avalanche could have unintended consequences. 

Continue to dig snowpits identifying and testing for PWLs in the snowpack, especially in areas further east of the crest with a shallower snowpack and on northerly aspects in the Washington Pass zone below the 1/17 crust. 

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

Weather and Snowpack

An atmospheric river arrived over the Northwest 1/17 forming a crust that is still referenced in observations regarding the persistent slab problem. 

Strong NE-E winds have been seen 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 6-12 inches of snow accumulating along the east slopes closer to crest in the central-east and northeast zones, with lesser amounts at lower elevations and in the Mission Ridge/Blewett Area through 6 pm Saturday. A slight warming trend occurred Saturday, most pronounced mid and upper slopes. 

Recent Observations

North

Persistent slab has been re-listed in the northeast zone highlighting a 5 cm layer of facets roughly 10 cm below the 1/17 crust in the Washington Pass zone and in areas further east. This reactive PWL has only been found in isolated locations, in cold non-wind affected north facing terrain. No avalanche activity has been observed on this layer.

NWAC pro-observer Jeff Ward was in the Varden Creek drainage Saturday and found 15-20 cm of storm snow well bonded to a variety of snow surfaces with the new snow generally lacking a slab structure. Small storm slab avalanches were only observed on steep solar aspects, likely failing on the most recent sun crust. Wind slabs on lee northerly aspects were the main avalanche problem with skier triggered avalanches possible near and above treeline.  

Central

Jeff Ward was at Cannon Mountain off of Icicle Creek Monday 1/30. He found a variable and shallow snowpack that ranged from 1 to 2 m, depending on elevation and wind affect. Many windward slopes had been scoured to the 1/17 crust with thin wind slab present on lee slopes. The 1/17 crust was down 20-40 cm but no avalanche activity was observed on this layer. Large surface hoar was found at all elevations in non-wind affected terrain.

Both Tom Curtis and Jeff Ward traveled independently in terrain east of Stevens Pass Wednesday 2/1, covering the areas of Rock Mountain, Jove and Union Peaks. Both reported rapidly forming, very touchy wind slabs by mid-morning Wednesday. Wind slabs were building much further downslope due to the strength of the winds. Wind slabs up to 12 inches were seen and noted forming well below treeline. 

South - No observations