Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Lots of new snow, recent avalanches, and frigid temperatures should all give you pause on Tuesday. As you ascend in elevation, think about avoiding terrain such as the base of cliffs, convex slopes, or confined gullies where avalanches are more likely. At upper elevations be on the lookout for wind-loaded slopes where larger avalanches could still exist.

Problemi valanghivi

  • Wind Slabs

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

    On Tuesday, you could be dealing with Wind Slabs of different ages. It won’t take much wind for you to be dealing with some freshly built Wind Slabs. These slabs should be shallow and easier to identify by looking for textured snow surfaces or actively blowing snow. Older Wind Slabs from the recent storm may be a bit more difficult to identify, so look for large drifts or freshly built cornices as indicators as to which slopes may be wind-loaded. If you feel stiffer or hollow-sounding snow under a few inches of light snow, that may be an indication that you are traveling on wind-loaded terrain. Although older slabs could be more difficult to trigger, if you do, the resulting avalanche will probably be large enough to bury or kill you. Take extra time to evaluate terrain features where Wind Slabs like to form such as at the base of cliffs, sides of gullies, convex rollovers, or in rocky chutes.

    (12/27/2021)

    The crown of a large avalanche in the upper Chair Peak Basin. The crown is estimated to be 2-3 feet deep, likely ran on the night of the 25th, and the debris filled a terrain trap near a common travel route for backcountry tourers and climbers. It is suspected to be a Wind Slab.

    Photo: Robin Pendery

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    In the simplest of terms, the sheer volume of snow accumulated over the past few days could be hazardous. We continue to receive reports of shallow and isolated soft slabs, which is why we are categorizing these new snow problems as Storm Slabs. Depending on where you are recreating, Dry Loose avalanches could also be a fit to capture the hazard presented by the recent storm snow. The management of these two issues should remain largely the same, regardless of your categorization of them. You can look at the upper snowpack to see if you are dealing with slabs or loose snow by using upslope tests to look for cracking, or quick hand pits and test slopes to look for failing blocks of snow. These signs would all point toward slab avalanches compared to loose avalanches. No matter which problem you are dealing with, be suspect of slopes over 35 degrees where loose snow could knock you off your feet.

    (12/27/2021)

    Multiple shallow soft slabs were observed throughout the Alpental Valley on 12/27. Often, they were interspersed with loose avalanches, making it difficult to discern between the two.

    Photo: Andy Harrington

Avalanche Discussion

On Monday, a beautiful morning gave NWAC personnel the opportunity to head up the Alpental Valley to look for recent avalanches and take stock of conditions. Signs of recent avalanches were not hard to find. Almost anywhere you looked there was a small avalanche that had been triggered by snow shedding from trees or rocks. Some of these avalanches were shallow soft slabs while others were loose avalanches. A large avalanche suspected to be a Wind Slab that was reported to us on 12/26 was visible in the upper Chair Peak basin with an estimated crown depth of 2-3 feet. Its debris pile filled a natural terrain trap and crossed a common travel route. A slight sun crust was reported to have formed on sunny slopes by day’s end.

Avalanches like the ones described above could be harder to trigger on Tuesday, but that isn’t a guarantee and does not mean that you should ignore these signs. The cold temperatures are slowing the healing process of the snowpack and any snow above the Solstice Crust could be in play for potential avalanches given the right trigger. That trigger could be you, a freshly built cornice, or hanging blocks of snow and ice that have accumulated on trees and cliffs. We know that there are multiple storm interfaces and even weak snow within the snowpack. Take the time to do your homework before stepping into consequential terrain.

Dress warmly and be sure to keep your partner in sight. The snow is still deep and soft, which creates a hazard, particularly near treewells. You can read more about these hazards here.

Regioni coperte