Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

The avalanche danger is generally Low on terrain not experiencing direct sun. Keep tabs on areas above you that are warming in the sun, especially if traveling in alpine terrain. Scattered wind slabs could be found on the highest peaks.

Problemi valanghivi

  • Loose Wet

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

    Loose wet avalanche activity continued Saturday to the north. Though most reported avalanches were above treeline, small natural and human triggered avalanches, plus other signs of instability were seen at mid-elevations as well. The pattern of sun and moderate temperatures will continue through the weekend. Though many slopes have already slid, some have not. Warmer than forecast temperatures could make for more significant avalanche activity. Wet avalanches are unlikely if the snow surface is frozen or partially melted. 

    When you observe signs of instability like rollerballs, pinwheels, or very small avalanches, limit your exposure to terrain experiencing direct sun. Stay away from steep slopes if you find yourself in thick, sun warmed snow as well. The greatest danger will be in large, south facing avalanche paths where smaller avalanches have a greater chance of entraining additional snow and even triggering a slab. Confined terrain like gullies and other drainage features below big, south-facing slopes are also at greater risk. Don’t linger . . . 

    (3/5/2022)

    Natural and skier triggered loose wet avalanches on a south aspect of Mt. Herman. Activity occurred March 3rh through 5th.

    Photo: Lee Lazzara

Avalanche Discussion

In addition to wet avalanches, small wind slabs might be found above treeline. Transport from moderate northerly winds was noted on the upper reaches of Mt. Baker, Shuksan, and other high peaks of the Cascades. With limited observations, it is up to you to assess stability as you gain elevation. Anticipate higher danger in wind loaded or sun warmed terrain and mitigate uncertainty by avoiding steep and unsupported terrain features.

A cycle of loose wet avalanches to D2.5 occurred on southerly aspects in West North March 3-5. Observed avalanches appeared to involve only the top layer of new snow and did not entrain deeper layers of wet snow. Little avalanche activity was noted in Stevens and Snoqualmie Passes the past three days. Weather station data points towards the conclusion that West Central received more rain than snow at below and near treeline elevations during the parade of storms earlier in the week. While areas farther north continued to accumulate new snow and have seen a bigger loose wet cycle, West Central likely experienced peak loose wet activity during prior rain events. The outlier to this is at the highest elevations that have many feet of new snow and could be reactive to a few rounds of strong sun and higher afternoon temperatures.

The biggest snowpack variable is elevation. At lower elevations, there is 0-15cm of recent snow above rain affected layers created by last weeks atmospheric river. Higher up there is 30-40cm over the first rain affected layer with generally more dry and less wet snow as one climbs higher or gets closer to ridgelines. Near treeline in West North, the February 14th crust was observed down 140-180cm and the late January crust layers are down a good 200cm or more. Snowpack testing has yielded few results. Colder temperatures on the horizon will only make the snowpack stronger.

Surface conditions vary widely from slope to slope with a mix of breakable crust, pockets of deep, grabby sun-softened snow, extensive avalanche debris, and even settled dry snow on north aspects above treeline. Expect to see suncrust farther into true east and west aspects due to higher March sun

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