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RegisterDec 4th, 2016–Dec 5th, 2016
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Cold temperatures will help preserve recent storm snow instabilities found on wind loaded aspects near and above treeline. In steep terrain where the new snow lacks a slab structure, watch for small loose dry avalanches near terrain traps like cliff bands where even small avalanches can have big consequences.
A few inches of low density snow may accumulate Monday mainly near the Cascade crest with little impact on the avalanche hazard. Westerly ridgetop winds are forecast to decrease Sunday night, but before then plenty of new low density snow is available for transport to lee aspects. Shallow storm or wind slabs should be less sensitive on Monday, but sustained cold temperatures will help preserve recent storm snow instabilities. In particular watch for lingering storm or wind slab on lee aspects near and above treeline that can still be human triggered. Only wind slab will be listed in the avalanche problems moving forward.
In steep terrain where the new snow lacks a slab structure, watch for small loose dry avalanches near terrain traps like cliff bands where even small avalanches can have big consequences.
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
A front crossed the Cascades Friday but likely only produced an inch or two of new snow near the Cascade crest with no accumulations further east. Moderate westerly ridgetop winds continued on Saturday.
A much stronger front sagged south across the area Saturday night delivering 8-10 inches at the Harts Pass and Lyman Lake Snotels respectively, 7 inches at Holden and Blewett Pass and 3-4 inches at Mission Ridge through Sunday morning. This system also ushered in the coldest air mass of the season.
Avalanche problems should be confined to the most recent storm snow and we are not tracking any weak layers in the lower or middle of the snowpack at this time.
Recent Observations
During midweek NWAC pro-observer Jeff Ward was in the Washington Pass area and found generally good ski conditions and a stable snowpack. Stubborn and shallow wind slab existed near and above treeline. Thin coverage and open creeks continued to be a travel hazard at the pass elevation.
On Friday Jeff was out again on Jove Peak east of Stevens Pass which can be representative of the east slopes closer to the Cascade crest. He saw no signs of instability but noted minor wind transport along the ridge.
In general more snow is needed in the Mission Ridge area to present an avalanche hazard. In wind-loaded terrain near and above treeline, no weak layers of note have been reported by the pro-patrol through Saturday.