Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

6-12" of new snow along with 20-40 MPH winds out of the West will create sensitive slabs of wind deposited snow above 7000 feet. As snowfall increases throughout the day, wind-sheltered areas may harbor softer slabs of storm snow below 7500 feet. New snow will be falling on slick surfaces, such as melt-freeze crusts, especially on south-facing slopes.

The avalanche danger will rise throughout the day today.

Problemi valanghivi

  • Wind Slabs

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

    A winter storm began moving through the region early this morning. Anywhere from 6-12" of snowfall is expected by this evening at upper elevations. Winds are forecasted to blow steadily today out of the west at 20-30 MPH with gusts into the 40-50 MPH range. As of 6 AM this morning, Tamarack Resort weather station already reported a wind gust of 62 MPH. With high snowfall rates and strong winds, you are likely to encounter sensitive slabs of wind-deposited snow above 7000 feet, especially on east-facing slopes.

    When the winds become this strong, loading can occur in unusual ways. Strong winds can blow snow much farther down a slope, especially below ridges. Local terrain can alter prevailing wind patterns and winds can change direction depending on localized terrain features. Stay attuned to changing snow conditions today. Avoid areas where the wind has deposited snow into dense slabs, particularly on east-facing terrain just below ridgelines. Look for clues like shooting cracks, sounds like whumpfing, or recent drifts or pillows. These clues are indicators that wind slabs are present and you should find another aspect to ride or ski. 

  • Storm Slabs

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

    6-12" of snowfall is expected to fall throughout the day and into the evening. As snowfall stacks up today, you can expect to encounter sensitive slabs of storm snow in wind-protected areas below 8000 feet. Although this storm came in warm and will be exiting cold (referred to as "rightside up"), there will likely be density changes within the new storm snow that could create poor bonding today. This new snow is falling on a variety of snow surfaces from the past week. We have melt-freeze crusts, rime or humidity crusts, facets, and wind-scoured snow. These existing snow surfaces will make it difficult for new snow to bond well, especially on south-facing slopes where a 3 cm (1.5") melt-freeze crust exists (see video at right).

    If you seek out wind-sheltered areas (good luck!) to avoid problem # 1 (Wind Slabs), you may likely run into problem # 2 (Storm Slabs). Look for clues like shooting cracks or sounds like whumpfing. These clues are indicators that sensitive slabs exist and strong snow is overloading weak snow. Your best way to avoid a storm slab avalanche will be to avoid slopes steeper than 30 degrees today.

Avalanche Discussion

Today's avalanche forecast is sponsored by Franklin Building Supply of McCall. Thanks for supporting the Payette Avalanche Center.

The winter storm that will be impacting our region today has been downgraded. Snowfall accumulations are forecasted to be less than previously expected but the wind forecast remains the same. As of 6 AM this morning, Brundage Resort received 1" and Tamarack Resort received 5". Snowfall began around 3 AM and is predicted to be spotty. Certain parts of the advisory area may see 12" or more, while other areas may see 4-8". West winds blowing 20-30 MPH with gusts near 50 MPH are forecasted to be widespread throughout the region. The avalanche danger will rise throughout the day.

Over the past ten days, we've seen very little snowfall and a stretch of mild, sunny weather. Melt-freeze crusts formed on aspects East through West, especially SE, S, and SW. We also found melt-freeze crusts on some aspects that tipped to the north. These crusts were buried just over a week ago. We saw cold temperatures for several days before receiving small amounts of snowfall. This weather pattern has allowed faceting (weakening of snow grains) to take place above and below some of these crusts. Weak snow near a crust is a potential recipe for an avalanche. The only other ingredients needed are a slab (building right now) and a trigger (hopefully not you). Snow does not like sudden changes and the weather events of today are indeed a rapid and sudden change. The terrain navigation skills required to steer clear of wind slabs and storm slabs will challenge the most experienced people today. If you feel like you don't have these skills, stick to terrain less than 30 degrees and give the snow time to adjust to these changes.