Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

You can still trigger a large slab avalanche that will probably ruin your day. Steer away from steep, unsupported, complex terrain. Favor planar slopes with shallower angles to get your powder fix while also reducing the risk of triggering a large avalanche.

A snow immersion accident resulting in a fatality occurred in backcountry terrain on Wednesday. Keep your partners in sight at all times. Stay close enough to help them if they get buried in a tree well or some other deep snow hazard

 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–2.5

    The likelihood of triggering a large, widely propagating, or surprising avalanche is lowering. That being said, poor snowpack structure still exists with faceted snow lurking 2-4’ below the surface. 

    If you were to trigger one of these avalanches it would be . . . 

    • Where there is less new snow over the faceted layer, like in wind scoured areas  - possibly easier to trigger
    • On very unsupported slopes like steep convex rolls or terrain above cliffs - more stress at the slab-weak layer interface
    • In less traveled terrain where there is less information about stability
    • If you put down a big load on a slope like multiple snowmobiles or a big group of people 

    Risk tolerance will probably determine what kind of terrain you get into this weekend. Avoid steep slopes if you want to be absolutely sure you won’t trigger an avalanche. If you decide avalanche terrain is on the menu, stick to planar, moderately angled slopes with no consequences in the runout below like rocks, cliffs, gullies, or other terrain traps. If you are unfortunate enough to trigger one, at least there will be a better chance you won’t get hurt. 

    (12/6/2022)

    This large, human-triggered avalanche failed at a layer of faceted snow. While much of the surrounding terrain was quite tracked up with no results, this steep, unsupported slope still produced an avalanche. Austin Pass/Table Mt, northwest aspect at 4700'.

    Photo: Matt Lubar and Phil Straub

Avalanche Discussion

On Friday, many loose snow avalanches up to D1.5 in size were observed in the Baker Backcountry. While quite a few were from the day before, continued traffic in steep terrain along with sun-warmed cliffs and trees produced another round. If you descend steep terrain, stay alert to snow moving with you. If we have any sun this weekend, look for additional loose snow avalanches below cliffs and other terrain warming in the sun and shedding snow onto slopes below.

No active wind transport, signs of wind drifted snow, or fresh wind slab were reported as of late Friday afternoon. You might find different conditions if you venture up into the highest alpine terrain or are farther east and south in the forecast zone. Textured or scoured snow surfaces, cornices, and wind lips will point towards slopes holding freshly wind drifted snow. Track changes in snow stiffness and use simple tests like hand shears and slope tests to identify and evaluate wind drifted snow.

On average there's three or more feet of right-side-up snow over the old snow surface buried on January 30th. This snow sits directly on crust in terrain that saw strong sun and warming from January 26th through 29th. On more shaded slopes, the new-ish snow lies over a layer of faceted snow over a crust - now decomposing - that formed closer to the new year.  More faceted snow is found below these crusts on all aspects. Avalanche activity related to these layers peaked last weekend with no new avalanches reported in the last five days. Snowpack testing still points towards propagation in layers of faceted snow.

 

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