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RegisterJan 29th, 2016–Jan 30th, 2016
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The main problem has now shifted to new snow instabilities, above the new rain crust. New areas of wind slab on lee wind exposed terrain, near and above treeline. Wind slabs may have formed on a variety of aspects due to highly variable wind directions. Watch for new cornices near ridges.
Cool weather with light snow showers and moderate westerly winds Saturday should allow for an overall slowly decreasing danger. Weak lower density snow that may exist above the new crust will slowly settle, but remain reactive to human triggers Saturday.
The greatest avalanche problem should be sensitive wind slabs on lee slopes, mainly NW-N-SE facing slopes, especially below ridges, near and above treeline.
Watch for newly formed cornices along ridges as well. These may be sensitive to human triggers.
Below treeline, the old wet snowpack should continue to drain, and slowly refreeze.
Non avalanche related hazard: Watch for newly opened creeks which may be quite deep in areas, below treeline.
Weather/Snowpack
Two fair weather periods earlier this month allowed surface hoar and near surface faceting to occur. These persistent weak layers were buried intact on January 3rd and 11th. Two heavy rain events, one a week ago and one late Wednesday into Thursday have likely eliminated the January persistent layers and they will be removed from the avalanche problems along the west slope zones.
The recent rain event should give the snowpack a new horizon going forward.
Mild weather, freezing levels approaching 8000 feet and rain in the Mt Baker area caused increasing wet snow conditions a week ago, followed by another heavy rain late Wednesday and early Thursday of this week. The rain finally changed to snow as snow levels dropped through the day Thursday with temperatures lowering some 10 degrees or more through the day.
Another strong, but colder front Friday deposited 6-12 inches of new snow along with very strong winds by late Friday afternoon. Some areas are reporting a strong bond to the new crust and some a poor bond depending on when new snow arrived. However, even where good bonding exists, there may be sensitive weak layers just above the crust, which formed before strong winds arrived Friday. These layers may make for some sensitive triggered slabs and will take a bit of time to settle and stabilize.
Recent Observations
NWAC pro-observer Simon Trautman ventured a ways into the white out conditions in the Baker BC Friday afternoon to test the new storm snow. New sensitive wind slabs were quickly forming on a variety of exposed aspects near treeline, during heavy snowfall rates and very strong westerly winds. Drifts were 8-18" and increasing. There is an intact layer of low density stellar crystals just above the crust forming the weak layer and reactive to skis on wind loaded terrain. Image below.
New sensitive wind slabs forming in the Mt Baker backcountry Friday afternoon 1/29. S. Trautman
Other observations received Friday afternoon from patrol at Alpental, indicated the crust had already formed prior to significant snow accumulations, so bonding was poor. Winds were very strong and limited consistent uniformed slab formation.