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RegisterDec 1st, 2017–Dec 2nd, 2017
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Fresh areas of shallow wind slab may develop near ridges Friday night and Saturday near and above treeline. Shallow storm slabs will most likely be found in the Paradise area by later in the day. Early season terrain hazards still exist, such as poorly covered rocks, vegetation and creeks, particularly at lower elevations.
Generally light and scattered showers Saturday morning should transition to more widespread shower activity in the afternoon. Showers are expected to be heaviest in the Paradise area Saturday afternoon and evening. See the NWAC mountain weather forecast tab for more details.
Fresh areas of shallow wind slab may develop Friday night and Saturday near and above treeline. Shallow storm slabs will most likely be found in the Paradise area by later in the day. Early season terrain hazards still exist, such as poorly covered rocks, vegetation and creeks, particularly at lower elevations.
Warm, wet weather before Thanksgiving caused wet snow and glide avalanches as well as significant snowpack consolidation. There are no snowpack concerns below the Thanksgiving crust and in general new snow received post-Thanksgiving has reportedly bonded well throughout the range.
During the week, a series of frontal systems have generally produced light amounts of the new snow for the west slopes of the Cascades. The exception is in the Mt. Baker area who received about 3 feet of snow this week including roughly a foot during the day on Friday. No significant avalanche activity has been observed outside of the Mt. Baker zone.
Observations
North
On Thursday, Mt. Baker pro-patrol triggered isolated pockets of wind slab about 20 cm (8") deep during control work. Also on Thursday, guides in the Mt. Baker area reported about 85 cm of recent storm snow above the Thanksgiving crust bonding well to the crust and within recent storm layers. However, active wind loading was occurring on north facing aspects around 5000'.
By Friday, steady snowfall led to widespread and very touchy wind and storm slabs on all aspects and elevation bands on terrain ~35 degrees or steeper. NWAC observers in the Mt. Baker backcountry reported average slab depths of 30 cm in sheltered areas and about 1 meter of snow above the Thanksgiving Day crust. Winds were gusty and distributing snowfall onto all aspects.
Central
Wednesday in the Alpental backcountry, NWAC observer Ian Nicholson found areas of unreactive wind slab on some east facing terrain features near ridges. Daytime solar warming had allowed surface snow to consolidate and form shallow storm slabs, but no avalanches were observed or triggered.
On Thursday, NWAC observer Jeff Ward found about 40 cm of settled snow well bonded to the Thanksgiving Day crust in the Stevens Pass backcountry. With good visibility, no avalanche activity was noted in the surrounding terrain.
South
On Thursday in the Crystal backcountry, NWAC pro-observer Dallas Glass found 25 cm (10") of this week's storm snow bonding well to the stout and fully supportable Thanksgiving rain crust. Shallow wind slab averaging 10-15 cm (4-6 cm) thick was found below ridges on W-N-E aspects, but was isolated in distribution. Total snow depth in this area peaked at about 1 meter at 6000' and above. NWAC pro-observer Jeremy Allyn found similar conditions on Friday and noted the lack of cornice formation along ridges.