Lawinenlagebericht

West Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
3 · Erheblich
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Kernpunkte

Updated 7:30 am: Increased danger rating to High due to higher snow totals than originally expected. Travel in avalanche terrain is not recommended.

Very dangerous and unusual avalanche conditions exist. Heavy recent snowfall and strong winds will create natural avalanches Sunday. Avoid open slopes 30 degrees and steeper and stay far away from avalanche path runout zones.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    2

    The West Central zone received 1-2ft of new snow overnight Saturday as a Puget Sound Convergence Zone took aim at Barlow Pass. Natural avalanches are likely and fresh slabs of new and wind drifted snow will be primed for human triggers on steep slopes in all elevation bands. Observers in the adjacent West North and Stevens Pass zones reported touchy conditions Friday and Saturday and widely propagating natural and triggered avalanches. Surface snow avalanches will continue to be large enough to bury, injure, or kill a person, and could even trigger deeper instabilities as they run downslope resulting in unsurvivable avalanches. Carefully assess new and wind drifted snow as you travel and watch for recent avalanches, shooting cracks, and collapses. Avoid steep open slopes and minimize your exposure to overhead hazard.

    (2/5/2021) Snowmobile triggered avalanche in the Mt. Baker NRA at the toe of the Easton Glacier on southerly aspect near 5000ft. The snowmobiler was caught by the avalanche and carried a short distance with their snowmobile partially buried. The avalanche looks to have failed 6-12in deep on the 2/4 interface with an impressive crown breaking several hundred feet wide.

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    A widespread natural avalanche cycle occurred during the storm January 30 - February 2. Numerous avalanches broke 3-4ft+ deep on a weak layer above a prominent crust (mid-January crust/facets). Avalanches grew very large (D3), had wide propagation wrapping terrain features, and ran far distances hitting valley bottoms. A handful of avalanches were human triggered on this layer Wednesday.  Observers in the West North zone Saturday targeted this layer with snowpack tests and found unstable results (see photo below). 

    The potential for natural and triggered deep persistent slab avalanches exists above 4000ft on slopes 30 degrees and steeper. This is not a problem to try to outsmart. These conditions are difficult to manage and tricky to accurately assess. You can use snow profiles and snowpack tests to track these layers, but not necessarily as decision-making tools as what you find on one slope may be different from the next. Build in a wide margin for error and stay away from steep open slopes.

    (2/3/2021) Very large avalanches ran naturally on Mt Herman during the storm cycle between January 31 and February 2.

Avalanche Discussion

The past two weeks were very active throughout the region with impressive storms, eye-opening avalanche cycles, and a few close calls. Avalanche conditions related to new snow and wind are concerning enough, and a lingering deep slab instability poses uncertainty and high consequences. Very dangerous and unusual conditions still linger as additional heavy loading from new snow and wind stress the snowpack further. The recent storm snow needs time to settle and stabilize, and deeper weak layers will require patience and a very conservative mindset. Only simple, low angle terrain is appropriate at this time.  

Beginning January 24, incremental loads of light snowfall buried a weak old snow surface (mid-January crust/facets) that formed during a prolonged period of cold, clear weather. Observations January 25-29 indicated the old snow surface to be problematic in isolated areas, but avalanches within new and wind drifted snow were more widespread. Heavy loading from new snow and wind January 30 - February 2 (4ft of snow/8.5in water at Heather Meadows) finally pushed the mid-January crust/facets to a tipping point and caused a natural cycle of deep slab avalanches large enough to destroy a house or break mature trees. With clear skies on February 3, many long time locals and professionals were able to document the aftermath, reporting avalanches in areas they had never seen run, and avalanche paths producing slides larger than they can remember. Several close calls occurred in the neighboring West North zone including snowmobile triggered avalanches breaking 3ft+ thick and several hundred feet wide in Canyon Creek on February 3 (photo below), and very large natural avalanches on February 1 on Mt. Herman's east face hitting Bagley Creek with debris and powder clouds running uphill across the valley towards nearby skiers (video below). 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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