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RegisterDec 6th, 2016–Dec 7th, 2016
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A slow improvement should continue, but locally increasing east winds near the crest may begin forming new sensitive slabs on lee, mostly westerly facing terrain, especially below ridges. In the steep wind sheltered terrain, watch for small loose dry avalanches near terrain traps like cliff bands where even small avalanches can have big consequences.
Partly cloudy conditions with cold temperatures are expected through midday Wednesday. This weather should allow for continued very slow settlement of any wind slabs recent formed, allowing for a slow decreasing trend in the avalanche danger overall.
By midday Wednesday and into the afternoon, however, expect increasing easterly winds nearer the crest. Watch for locally increasing winds later Wednesday as the very low density surface snow will be easily transported to lee slopes or cross loaded features and shallow wind slabs may form quickly in exposed terrain.
In particular, watch for lingering or newly forming wind slab on lee aspects near and above treeline that may be sensitive to human trigger.
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 crossed the area Saturday night, depositing 8-10 inches recorded from 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. Cool light showers Monday through early Tuesday only added very light additional snow amounts, not affecting the danger.
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
The most recent observations from near Washington Pass Sunday and again Monday, indicated a favorable snowpack profile with no triggered avalanches noted and good bonding to the older snow layers. Some minor wind effects were noted but most areas upper snowpack lacked a slab character, with mostly low cohesion powder providing excellent conditions!
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.
While some of the coverage below treeline remains thin, the upper elevations of this lowest band are filling in quite impressively and we are bumping the overall danger to moderate in this band as a result. The lower elevations in many areas lack good coverage and open creeks and other early season hazards remain.
On Friday Jeff was out again at Jove Peak east of Stevens Pass, which can be representative of the eastern 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.