Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Dangerous avalanche conditions linger. You can easily trigger large avalanches within new and wind drifted snow at upper elevations. Conservative terrain selection remains critical as deeply buried weak layers need additional time to heal.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2

    The 2ft of new snow that accumulated in the Mt. Baker area over the weekend needs time to settle and stabilize. Even though precipitation will taper off by Monday, fresh slabs of new and wind drifted snow will be primed for human triggers, especially on steep upper elevation slopes. Observers recently reported touchy conditions 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 deep weak layers 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. Continue to choose lower angled terrain and avoid exposure to wind-loaded alpine slopes above.

    (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

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    The potential for lingering 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. What you find on one slope may be different from the next. Use snow profiles and snowpack tests to track these layers, and place your results within the context of a bigger picture of conditions. As this layer takes additional time to heal, build in a wide margin for error and stick to low angle terrain free of overhead hazard.

    A widespread natural avalanche cycle occurred during the storm from 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 (2/3).  Observers in Canyon Creek Saturday (2/6) targeted this layer with snowpack tests and found unstable results (see photo below). 

    (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 in the West North zone 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. The recent storm snow needs time to settle and stabilize, and deeper weak layers will require patience and a very conservative mindset.

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 (D3+). 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 also occurred 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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