Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Forecast Update:  Upgraded the Below Treeline elevation band to Considerable due to an increase in forecasted precipitation totals.

Warming temperatures, snow, rain, and strong winds will create very dangerous avalanche conditions. This is a good day to avoid avalanche terrain, especially in higher elevations where very strong winds will build deeper slabs. Expect significant variability throughout the zone and rapidly changing conditions.

Problemi valanghivi

  • Storm Slabs

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

    Significant precipitation with warming temperatures will create upside-down storm snow with heavy, dense snow on top of lighter, softer snow. This heavier snow will slide easily on the lighter snow beneath. Slabs will form on all aspects and elevations, the distribution of unstable snow will increase rapidly with elevation and in areas closer to the Cascade Crest. Avoid avalanche terrain in areas near and above treeline. Below treeline, choose conservative terrain to avoid the high consequences of being caught in small avalanches where you could be carried over and into many obstacles.

    Strong winds will build deeper drifts of snow on lee aspects, avoid traveling near ridgelines or in open terrain that is wind affected. 

    Storms such as this are an excellent time to look for bullseye data to inform you that the snowpack is unstable and avalanches are likely. Look for recent avalanches, blowing snow, or shooting cracks. Any of these signs are an indication that you should stick to low-angle slopes.

    Using your ski pole to probe the snow is a good way to identify strong over weak snow. 

    Photo: Tom Penoyer

Avalanche Discussion

A mixed bag of stormy weather is in store for the PNW, including heavy snow, freezing rain, rain, and strong winds. With this storm impacting our mountains, avalanche danger will increase rapidly. Warming temperatures will make it easy to trigger storm slabs in the new snow. At upper elevations, strong winds will be blowing snow around and quickly building unstable wind slabs. With winds up to 40-50mph, deep slabs can be created on all aspects and sometimes in places further down from ridges than expected. If precipitation switches from snow to rain, wet loose avalanches will also be a possibility on Saturday.  If you brave the stormy conditions, stick to low-angle slopes in wind-sheltered terrain. 

In areas in the northern portion of this zone, weak snow may be lingering above crusts, creating the potential for larger avalanches. We have limited data from these areas, approach terrain slowly and cautiously. Use snowpack tests to determine how well bonded the overlying snow is to these crusts. 

Most areas in the zone have a significant snowpack, though some still lack significant coverage to produce avalanches. We have little information and a lot of uncertainty about the snowpack structure near and above treeline. There is a lot of variability throughout the zone, and a more substantial snowpack exists in the western portions. An observation from the Wenatchee Mountains shows that unstable snow exists even in areas with limited snowpack. The previous few days of moderate to strong winds created wind slabs on lee aspects and scoured windward aspects nearly to the ground. Expect that avalanche danger will vary throughout the zone and will increase rapidly during the day.

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