Avalanche Forecast

Continued light storm snow deposits overnight Sunday should give way to partial clearing Monday as high pressure affects the area. Winds should be light Sunday night and Monday with further cooling.   

While the ending showers with light winds and cold temperatures should lead to an overall improving avalanche danger Monday, there has been such significant storm snow, along with periods of moderate winds over the past three days, that another day or more of very cautious travel in backcountry terrain is urged.

Storm and wind slabs should begin to slowly settle and stabilize beginning Monday. However, careful snowpack evaluations, cautious routefinding and conservative decision-making will remain essential, as these dangerous avalanche conditions slowly improve.

Be wary of the potential buried persistent layer of surface hoar or near surface facets, potentially in combination with a thin crust layer. A high degree of uncertainty exists as to the spatial variability of this layer and the sensitivity to human trigger as it is now buried 1-2 feet or possibly more as you travel nearer the crest. 

Choose low angled terrain and avoid slopes connected to avalanche paths with wind loaded start zones. 

Expect new wind slab near and above treeline in all zones, especially on lee easterly aspects. Avoid all wind loaded terrain Monday. In areas away from the crest, such as Blewett Pass and Mission Ridge, expect wind slab to be the primary avalanche problem on lee aspects near and above treeline. 

Loose dry will not be listed as an avalanche problem, but in steep terrain lacking a slab structure, continue to watch for small loose dry avalanches near terrain traps like cliff bands where even small avalanches can have big consequences. 

With deep unconsolidated snow in many wind protected areas, there remains an increased risk for tree well and snow immersion suffocation at this time. Ride or ski with a partner and keep them in sight at all times!

Even though the lower part of the below treeline band is filling in, watch for early season travel hazards such as barely covered rocks and open creeks.

Weather and Snowpack

An active and cool weather pattern has resulted in a snowy December thus far with NWAC stations along the east slopes recording about 1 to 3 feet of snow.

Cold and fair weather took hold midweek. During this time, there have been many reports of right side up, favorable density profiles with lower density snow nearer the surface. The Washington Pass area in particular has enjoyed excellent skiing and riding conditions with good stability and light winds. Widespread near-surface faceting and surface hoar formation had been observed particularly in this area of the east slopes. The Mission Ridge area experienced moderate easterly winds through Thursday night before switching to moderate westerly winds early Friday morning. Moderate westerly winds continued at Mission Ridge on Saturday. 

Light to locally moderate snowfall accumulated Thursday night through Saturday morning along the east slopes. Mission Ridge and Blewett Pass saw a few inches each day, but Holden Village and the Lyman Lake Snotel showed about 12-20 inches of new respectively. In the Southeast zone, Snotels averaged about 6-12 inches of new snow over the last 2 days ending Saturday morning.  A slow warming trend began Friday night and continued on Saturday, gradually dislodging the previous arctic air mass.  

Another few inches from snow showers likely accumulated Sunday, potentially more nearer the crest. 

Recent Observations

Mission Ridge pro-patrol reported the switch to westerly winds had loaded NE aspects below ridgetop on Friday. Easy to trigger wind slabs of 40 cm deep were observed on NE aspects around 6700 feet. Just a few hundred feet below in less wind affected terrain, the snowpack was generally right side up and lacked a cohesive slab. Avalanche concerns were confined to loaded slopes just below ridges again on Saturday in the Mission area. A shallow snowpack still locally limits the avalanche danger to the higher elevations and more wind loaded aspects.