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. 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. 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 a confirmed persistent weak layer from about December 8th in the Washington Cascades. This type of layer is less common at Mt Hood and it won't be listed here as an avalanche problem. We don't have any snowpack observations identifying a persistent weak layer at Mt Hood. But ratchet back your plans if you experience collapsing or whoomping. Some time and snowpack tests from many areas will be needed to determine to what extent this layer is 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 was seen early last week.

The latest storm cycle began about December 8th starting with a couple day warming trend as southwest flow eroded an Arctic air mass over the Northwest. The warming trend leveled off with temperatures staying well below freezing December 10th and 11th and snowfall tapered off by December 12th. NWAC stations at Mt Hood had about 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 with some avalanches releasing on the December 8th layer.

The Mt Hood Meadows pro-patrol Sunday reported triggered soft slab avalanches were sensitive and releasing 6-12 inches in areas previously controlled. However, control work in Heather Canyon for the first time since the storms began Thursday also produced soft slabs with up to about 1 foot crowns. By Sunday afternoon slopes that had released early in the morning were already reloading and producing ski sensitive soft slabs up to about 6 inches.

The Mt Hood Meadows pro-patrol on Monday reported mostly cold stable powder including in non-previously skied terrain. Limited 12-18 inch storm slabs were found on N-NE  slopes in teh 5500-6500 foot range.

A report is available via the NWAC Observations tab for the Tilly Jane drainage on Monday. Deep but generally homogenous storm snow was indicated with very small wind slab on a N-NE slopes near a ridge line.

A report is also available for Monday via Turns All Year for the Barlow Snowpark area with good stability in deep storm snow indicated.

By Tuesday the Mt Hood Meadows pro-patrol found only pockets of 1-2 foot wind slab on southeast slopes in the 6-7000 foot range with hand charges. A large result at a higher elevation was obtained with their howitzer but details are not yet available.