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RegisterDec 28th, 2017–Dec 29th, 2017
Olympics.
Human triggered avalanches will become more likely as denser storm snow continues to build over less dense older snow near and above treeline as snowfall intensities increase during the day Friday. Especially watch for building wind slab on a variety of aspects near and above treeline where either older less dense or newer denser snow has been transported onto lee slopes. As rainfall increases and moves to higher elevations tomorrow, watch for saturated snow and avoid consequential terrain features. Watch for changing conditions, travel conservatively and rein in your plans as conditions deteriorate throughout the day.
A second storm (Friday) on the heels of the first (Thursday), will bring significantly more precipitation and further warming than the initial system. The storm track that will bring moderate SE winds shifting to SW during the day, along with further warming, increasing precipitation intensities, and snow lines rising above ridge crest level (at Hurricane) late in the day. Sharp cooling and drying should arrive during the evening hours.
Wind and storm slabs will be increasing in size and likelihood of human triggering as slabs of increasing thickness build over the lower density, weaker, older snow prior to Thursday and become increasingly touchy by later in the day. Especially watch for building wind slab on a variety of aspects as winds directions shift during the storm. Wind and storm slab issues will be confined to increasingly high elevations as the rain/snow line works it's way to higher elevations during the afternoon hours.
On Friday morning, loose wet avalanches are mostly likely encountered below treeline on steeper slopes due to warming and light to moderate rain. By afternoon, loose wet avalanches will be found further up the mountains in the near treeline band. At higher elevations which have received more snowfall, the loose wet slides will be larger and and increasingly consequential. In general, when snow is becoming saturated, avoid complex terrain as loose wet avalanches will be much more dangerous.
Watch for changing conditions, travel conservatively and rein in your plans if conditions deteriorate faster than expected. See the mountain weather tab for weather forecast details.
Also despite all the new snow, early season hazards still exist at some lower elevation locales and especially around creek beds that are not filled in.
At Hurricane Ridge, the frontal system arriving Thursday evening brought a few inches of higher density snow at temperatures just below freezing, with light to occasionally moderate SW winds which transported some snow.
This new snow sits over the estimated 6 inches of lower density snow accumulation during the series of weak weather disturbances that traversed the area over the last week prior to Thursday.
The previous major storm cycle ended 12/19-12/20.
Observations
On Wednesday, a shallow loose dry avalanche on a northwest aspect in the Tunnel Path above the road ran 100 feet and knocked a skier off his feet. A pit nearby showed right-side-up snow.
A second hand report of at least one human triggered loose dry avalanche (sluff) caught a skier(s) on Sunday 12/25. No injuries were reported.
NWAC pro observer Matt Schonwald was at Hurricane Ridge on Saturday 12/24 and reported evidence of north to east winds but no wind slab or significant layers in the upper snowpack. The snowpack structure was generally right-side with good bonds to the Thanksgiving crust.