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RegisterDec 31st, 2016–Jan 1st, 2017
Olympics.
The 12/17 persistent slab remains a concern, although has become less likely to trigger. Avoid travel in open terrain and especially with large groups as these slides may require a larger load to trigger. Continue to avoid steeper slopes of consequence. New wind affected snow should be widespread on New Year's Day.
A passing front overnight should move south of the Olympics early New Year's Day. Generally light amount of new snow accumulation is expected by Sunday, however strong and shifting winds should redistribute any available surface snow to a variety of aspects.
New and lingering wind slabs will be the primary problem on New Year's Day. The 12/17 persistent slab remains a problem in the Hurricane Ridge area, but is becoming less sensitive to trigger.
While triggering a slab to the 12/17 interface has become less likely, the travel advice remains conservative. Avoid travel in open terrain and especially with large groups as these slides may require a larger load to trigger.
Wind affected snow should be widespread Sunday, especially with strong shifting winds, watch for wind transported snow on a variety of aspects and features.
Weather and Snowpack
A strong front and strong west flow aloft was seen over the Olympics and Cascades on Monday and Tuesday. The NWAC station indicated strong south to southwest winds Monday and Tuesday with almost 2 feet of new snow for the 48 hours ending Wednesday morning with a cooling trend.
A warm front caused moderate to strong winds and periods of light to moderate snow Thursday with about half an inch of water through Thursday evening at the Hurricane Ridge station. New snow initially fell during a warming trend with moderate S-SW winds, but stormy conditions quickly subsided behind the front Thursday evening.
A front has begun to deposit light amounts of new snow through the afternoon Saturday, 12/31 with increasing winds.
Recent Observations
NWAC pro-observer, Matt Schonwald was at Hurricane Ridge on Wednesday and reported the 12/17 PWL is still causing collapsing on all aspects especially in less skied areas below ridge lines. Recent natural wind slab releases of 10-12 inches were also seen on N-NE slopes below ridges at about 6000 feet. A 2-4 foot x 150 foot wide wind slab crown on the convex north slope below the visitor overlook was seen which may have released on a buried surface hoar layer from around Christmas Eve. The road to Hurricane was closed on Thursday.
On Friday, NPS rangers reported wind affected snow surfaces well below treeline with about 4" of dense new storm snow. No natural avalanches from Thursday or Thursday night were observed with good visibility Friday morning. Little loose surface snow was available for future transport.
There were two triggered avalanches Friday in the Hurricane area, including a solo traveler who was partially buried after triggering a soft slab avalanche and was fortunately able to self rescue.
NWAC pro-observer, Matt Schonwald was back in the field in the Hurricane Ridge area Saturday, 12/31. Matt found evidence of widespread wind transported snow near ridges and cross loaded features, cornices on multiple ridges and evidence of naturally triggered storm slab avalanches, likely during recent storms late last week. ?
In multiple test pits Saturday, the 12/17 PWL was found still intact buried consistently 60-80 cm below the surface. However, strong, well settled snow above and good bonding is indicating that triggering this layer is becoming unlikely.