Avalanche Forecast

We are going to keep the snow tap turned on for one more day with additional light to moderate snowfall Sunday night followed by a sharp cooling trend and light showers on Monday.

Moderate snow is expected for the central-east and southeast Cascades Sunday night and combined with a slight warming trend, this may cause a natural avalanche cycle in these zones overnight. Lighter snowfall is expected in the northeast Cascades with cooler temperatures.

Storm slab sensitivity may peak Sunday night particularly in the central-east and southeast Cascades, but may still be touchy Monday. While deeper storm slab instabilities should be healing, it is still possible to trigger a large storm slab avalanche in isolated areas closer to the Cascade crest.

Lingering wind slabs will be the primary avalanche hazard in the northeast zone near and above treeline. 

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. 

New snow instabilities will need more time to settle out so make conservative terrain choices by choosing lower angled terrain and avoiding wind loaded slopes near and above treeline. 

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 12-24 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 Sunday morning. Moderate W-SW winds occurred in the Washington Pass zone Saturday night. Light snow was beginning to increase Sunday afternoon in the southeast and central-east zones. 

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.  

On Sunday, Jeff and NCH observed debris from several small wind slab avalanches and one large wind slab avalanche, size D2.5, that ran from ridgeline over 2000 feet on a ENE aspect likely during peak precipitation and wind loading Saturday night. Storm slabs were not particularly sensitive in areas Jeff traveled, with evidence of a few previous natural storm slabs observed on steep solar aspects that likely ran on the 1/30 sun crust.  

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