Avalanche Forecast

On Tuesday, a frontal system will bring a rapid cool down with new snowfall accumulating above 4500-5000 ft by the afternoon. You may still trigger Loose Wet avalanches or they may be triggered by additional rainfall Tuesday morning. Watch for signs of wet snow conditions such as sluffing, roller-balling and any natural Loose Wet avalanches as signs of an increasing hazard. Loose Wet avalanches still have the ability to become large in areas where they gouge down to deeper layers of moist or wet snow. 

Shallow new Wind Slabs may form on lee slopes above treeline by the afternoon. Use visual clues such as fresh cornices, wind drifted pillows and cracks in the snow all indicating that you could trigger a Wind Slab avalanche. 

Large fresh cornices will still be fragile due to recent warm temperatures and initial rainfall Tuesday morning. Give cornices a large margin of safety and avoid travel on slopes below, as cornice failures may trigger large avalanches on slopes below.

Minimize or avoid exposure below unsupported slopes as the potential for Glide Avalanches will increase during prolonged rainfall and warm temperatures. 

Monday was warm with filtered sunshine. The dry weather followed the strong weekend storm which initially pushed rain into the near and above treeline elevations bands early Saturday. Cooling and significant new storm snow followed through Sunday afternoon with 1 to 2+ ft of snow above 4000-4500 feet. There was a significant snowfall gradient with elevation with this spring storm. Wet snow avalanches were seen earlier in the storm and continued at lower elevations through the weekend. New Wind and Storm Slabs developed at higher elevations later in the weekend with fresh cornices developing along ridgelines.   

Moist or wet snow can be found in the upper snowpack. The 4/1 firm crust may still exist in some areas, it has most recently been identified in the Crystal area 1.5-2 ft down. 

Out of the weak layers that we've tracked through the season, the 2/8 crust can still be identified in many areas 5-7 feet below the surface. This interface was associated with the 2/13 facets. Though it's unlikely, if significant water pools on the crust, it could result in very large and dangerous Wet Slabs.

Observations

North

On Friday, NWAC observer Jeremy Allyn traveled in the Bagley Lakes area. He reported many Wet Loose and Slab avalanches on north, east, and south aspects around 5,000 ft. Some were big enough to bury a person. He also found very wet snow in the upper 2 ft of the snowpack and challenging, wet travel conditions.

Central

Stevens Pass DOT and Stevens Pass Pro-patrol reported large and destructive avalanches during control work that released as soft slabs with explosives and quickly entrained wet snow at lower elevations on Monday. In a section of the ski area with minimal skier traffic on the east end of Cowboy Ridge, this explosive triggered slide (SS-AB-D2.5-R3-O) on a north aspect produced 4-5 ft of debris as it entrained old saturated snow below.  

Pro-observer Matt Primomo observed recent natural wet snow and storm snow avalanches in the Stevens Pass backcountry over the weekend, including this recent Litchenberg Wet Slab Avalanche on a SE aspect at 5200'. 

Pro patrol at Alpental Sunday reported about 1 ft of new storm snow that was sensitive to ski triggering, releasing soft slab avalanches of 8-12" and running long distances, entraining all the recent snow, running on the old wet snow surface. At lower elevations the new snow was easily releasing as Wet Loose avalanches by skis. 

South

NWAC professional observer Jeremy Allyn traveled in the Crystal backcountry Monday 4/9. Through mid-day, Jeremy found poor travel conditions as the surface crust quickly broke down with moist or wet snow in the upper snowpack.  Recent large Wet Loose and one Wind Slab avalanche from the weekend were observed in surrounding terrain.