Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Strong east winds formed fresh slabs at mid and upper elevations. Identify and avoid steep terrain features like convex rolls and unsupported terrain above and around cliffs holding recently wind drifted snow. Look for wind slabs where you don’t normally see them.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Thursday’s wind event had unequal outcomes for West North with some areas seeing minimal wind effect while terrain a ridge away got hammered. Natural and human triggered slabs were mostly limited to D1 in size but a few were larger. Some observers definitely backed off of steep convex terrain holding fresh wind slab. Alpine terrain generally saw more wind but the high west-facing flanks of Shuksan appeared to have avoided the worst of it.

    Unstable wind slabs will probably have a similar, scattered distribution Friday. Evaluate slopes on a case-by-case basis as some commonly loaded slopes could be slab-free while others will be a no-go. Wind slabs may be easier to trigger where they formed over a crust on solar aspects.

    Cornices and other clues that show the usual direction of wind loading - normally from the south and west - might not be useful to determine where fresh wind slab lurks. Instead look for recently scoured ridgelines with smooth, fat, or pillowy-looking drifts on the slope below. Test slopes and hand shears will help gauge wind slab reactivity and depth and can help you identify areas where they are easier to trigger. 

    (2/23/2023)

    Small wind slab avalanche on the south face of Goat Mt.

    Photo: NWAC Public Obs

Avalanche Discussion

AVALANCHE FATALITY: COLCHUCK PK, EAST CENTRAL ZONE: READ THE PRELIMINARY REPORT HERE.

 

Loose snow avalanches are another consideration for Friday and the type of instability you are most likely to see. Light-density snow in wind sheltered areas should still sluff easily despite storm snow settlement of over 50%. 

Warmer afternoon temperatures, light winds, and full sun will trigger signs of instability like rollerballs and even small avalanches. Keep an eye on steep terrain overhead as the day heats up and pull back if you see more activity than anticipated.

The latest storm produced a less common snowfall pattern due to westerly flow during the bulk of the precipitation. Weather stations on the flanks of Mt. Baker picked up 4-6” of precipitation from Feb 19-21 with 4-6’ or more of new snow near and above treeline. Heather Meadows and the surrounding area - usually the big winner when it comes to precipitation and snowfall - received a bit less with 2.8” of precipitation and about 2-3’ of new snow at treeline.

Avalanche activity varied as well. Widespread natural avalanches were reported from Schriebers/Mt. Baker NRA on Monday. Early Tuesday morning a large natural avalanche ran over 3000’ from high on the south side of the ridge connecting Church Mt. and Excelsior Pass down to below treeline (1900') and put a 10’ deep debris pile on Church Mt. Road. Natural slab and loose snow avalanches were observed Tuesday around the Baker Backcountry but the size and extent of avalanche activity appeared a step lower in number and size.

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