Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Several avalanches were reported in neighboring zones on Thursday, and more snow through Friday means avalanches will continue to occur. Your highest chances of triggering an avalanche are in wind drifted deposits of snow, although identifying these wind drifted areas may present a challenge. Investigating the top 2-3 feet of the snowpack for weaknesses in a snow pit and using small test slopes before exposing yourself to larger steep slopes is important if you're planning to get out onto steep terrain on Friday. 

Problemi valanghivi

  • Wind Slabs

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

    Several natural and human triggered wind slab avalanches were reported in nearby zones on Thursday. Some avalanches are failing as deep as the Solstice Crust, buried at the start of our current storm on 12/21. One to two feet of snow is present above that crust throughout the zone. Wind slabs could grow to several feet deep over the crust on Friday, and avalanches are likely with a human trigger. 

    Cooler temperatures, subtle winds, and a growing layer of concern mean that this light, fluffy snow could pose more of a challenge for identifying wind slabs.  Your usual clues such as identifying textured snow or pillows, or seeing shooting cracks may not be as obvious. Unless you are sure you're off wind loaded slopes, digging down to just under the solstice crust in a snowpit and  completing stability tests in representative terrain are your best bet at identifying the problem.  Get out onto small test slopes before exposing yourself to large steep slopes. If you aren't experienced with testing for instabilities with these methods sticking to slopes less than 35 degrees is a good call on Friday. We've got excellent low density snow right now, and travel on lower angle terrain will still make for a good time. 

    (12/23/2021)

    A small wind slab was easily triggered on an East facing slope at 5,400ft in the Stevens Pass Zone on Thursday.

    Photo: Matt Primomo

  • Storm Slabs

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

    Storm slab avalanches in non wind-loaded terrain are possible on Friday. This is especially the case in areas where the snow is not well bonded to the Solstice Crust. This slab is 1 - 2 feet thick.  Quickly investigate the new snow layer hardness and how well it is bonded to the solstice crust to determine whether avalanches might occur in the new snow layer. Use small test slopes before you expose yourself to large steep slopes. 

    As the fresh snow is cold and dry, small dry loose avalanches are expected in the surface snow layer. You could trigger a small loose avalanche as you enter a steep slope, or as you make your way down it. They will probably remain small in size, but remain alert for them if you travel in steep terrain. Most importantly, don't send one down onto another person beneath you. 

    Even small storm slab avalanches present a danger when combined with terrain traps.

    Photo: Lee Lazzara

Avalanche Discussion

We are currently amidst several days of unsettled weather which began Tuesday night.  We're going to keep getting snow at least through Christmas day.  Small and large avalanches are occurring in new layers of snow we're received since Tuesday, amounting to 1-2 feet of snow throughout the zone.  As snow continues to slowly add up, avalanches will gradually increase in size as well. 

We've received several reports of a "right side up" snowpack in non wind-affected areas. The "right side up" snowpack is usually attributed to cooling temperatures during the storm. Heavier snow with warmer temperatures falls earlier and then temperatures cool, with snow becoming lighter and fluffier, usually contributing to more stable avalanche conditions. Oftentimes this circumstance makes travel easier as well, where there is lighter snow at the surface to move through upon a heavier base beneath. 

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