Avalanche Forecast

A low pressure and frontal system should pass by to the south across Oregon and north California on Wednesday. It looks like this will system will cause light to moderate southeast winds in the Olympics and Cascades and mostly light snow over Mt Hood and the south Cascades on Wednesday. East winds will pick up in the Cascade passes and temperatures should stay cool on Wednesday.

Overall the avalanche danger will be less on Wednesday than the past few days. But small areas of new wind slab might be possible depending on the strength of the east to southeast winds.

New wind slab should not be extensive as east to southeast winds are not expected to be strong on Wednesday. But significant local transport is possible in places such as around Snoqualmie Pass. Since older wind slab is still possible on mainly north to southeast aspects and new local wind slab is possible on northwest to west aspects, wind slab will be indicated on all aspects. Watch for firmer wind transported snow which would be be more extensive if winds are stronger than expected.

Storm slabs from the recent storm cycle will further settle on Tuesday.

There is still uncertainty regarding the regional extent, spatial variability and the stability of the potential December 8th persistent weak layer which would be buried at about 2-4 feet along the west slopes. Ratchet back your plans if you experience collapsing or whoomping. Further time and snowpack tests from many areas will be needed to determine is this layer is still a regional problem.

Loose dry avalanches will not be listed as an avalanche problem on Tuesday. 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 a 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.

The regional avalanche danger is expected to further slightly decrease on Thursday.

Weather and Snowpack

Cold and fair weather early last week allowed for a sun crust to form on many solar aspects and for cold low density snow, near surface faceting and/or surface hoar to become fairly widespread.

These layers began to get buried in most areas on about December 8th when the latest storm cycle began starting with a couple day warming trend as southwest flow eroded an Arctic air mass over the Northwest. This initially buried the cold low density snow, near surface faceted snow and/or surface hoar with denser snow in most areas. The warming trend leveled off with temperatures staying well below freezing December 10th and 11th and snowfall tapered off by December 12th. NWAC stations along the west slopes had about 2-4 feet of snowfall for the 4 days ending Monday morning!

Recent Observations

A regional storm and avalanche cycle was seen about Thursday to Sunday especially along the west slopes with some avalanches releasing on the December 8th layer.

The Mt Baker pro-patrol Sunday reported widespread 18-24 inch natural storm slab avalanches on most NW-NE facing slopes along the Shuksan Arm though it remained uncertain how sensitive slabs were to triggering on more deeply buried persistent layers if present.

Professional observations at Snoqualmie and Stevens Passes Sunday found the December 8th layer buried at about 3 feet or more. Several field personnel experienced collapsing of this layer although the snow above lacked the significant slab character to produce avalanches at the test locations.

There was a snow immersion close call snow immersion fatality at Snoqualmie on Sunday and apparently at Stevens on Saturday. There was also apparently a full avalanche burial on Mt Herman near the Mt Baker ski area on Sunday but the party has not yet been contacted and we will see if any details become available.

Several reports are also available for the west slopes Sunday via the NWAC Observations tab.

Settlement and stabilizing occurred by Monday and Tuesday but backcountry reports are not available.

The Mt Baker pro-patrol reported more limited avalanche control results on Monday with only local new 7 inch storm slab on sheltered slopes.

The Crystal pro-patrol skied extensively in the backcountry on Monday while searching for a missing skier and noted recent settlement and no avalanche activity. The skier was later found by Highway 410.

By Tuesday the Mt Baker pro-patrol reported no signs of instability.