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 to moderate showers on Monday.

Heavier snow is expected for the south Cascades Sunday night and combined with a warming trend, this may cause a natural avalanche cycle in this zone overnight. Storm slab sensitivity may peak Sunday night but will continue to be touchy Monday. While deeper storm slab instabilities should be healing, it is still possible to trigger a large storm slab avalanche in specific areas.  Avoid wind slab on lee slopes near and above treeline Monday.

Be aware that small loose dry avalanches triggered on steep slopes can entrain deeper snow layers.   

New snow instabilities will need more time to settle out in this zone so make conservative terrain choices by choosing lower angled terrain and avoiding avalanche terrain near and above treeline. 

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 2-3 feet of snow pummeling the west slopes through Sunday afternoon. 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 Saturday but a slight warm-up occurred Saturday night with a switch to westerly flow. Sensitive but generally shallow storm slabs were reported throughout the west slopes on Saturday from ski area control work and some backcountry observations. Intense precipitation rates Sunday morning became light to moderate during the day. 

Recent Observations

North

Mt. Baker pro-patrol produced large storm slabs of 24-36" (60-90 cm) during morning control work and at least one natural storm slab avalanche was observed outside the ski area.  

Central

Stevens Pass ski area and DOT professionals reported very touchy storm slabs during control work Sunday morning. Some slabs broke into deeper storm layers from earlier in the weekend with up to size D2 or D2.5 slides observed. Loose dry avalanches in steeper terrain started small but quickly gouged down and entrained additional storm snow. Pro-observer Ian Nicholson was at Yodelin just east of Stevens on Sunday and found soft storm slabs propagating around 50 cm down in ECTs and easily ski triggered on short test slopes. Collapses within the storm snow produced whumpfing while breaking trail. 

Alpental pro-patrol found easily triggered storm slabs in and outside of their ski area with skier triggered storm slabs up to 50 cm. The storm slab in the photo below broke about 15-20 cm above the 1/29 rain crust in the Snoqualmie area.

Skier triggered storm slab photo from John Stimberis 2-5-17, Denny Mt 

South

NWAC pro-observer Dallas Glass was in the Crystal backcountry in Bullion Basin Sunday and found a reactive storm layer 35-40 cm down in snowpit tests on all aspects below and near treeline. Shallower storm slabs could be triggered on test slopes. Storm snow from this cycle had settled to about 60-65 cm. No natural avalanches were observed and recent wind transport was localized to near the ridgeline.