Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
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Pericolo valanghe

Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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In sintesi

Rain falling below 7000 feet will cause wet loose avalanches 1-2 feet deep today. Heavy snow and strong winds will build sensitive wind slabs and will likely overload persistent weak layers buried in our upper snowpack. Dry slab avalanches are likely above 7000 feet and could be large and destructive. Wet and dry avalanches forecasted for the same day is unusual and traveling in the mountains will require extremely cautious navigation today.

Problemi valanghivi

  • Wind Slabs

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

    Heavy snow began falling around 4 AM this morning. As I write, some areas around 6500 feet have already accumulated 4-6 inches of heavy snow. Another 3-7 inches of snowfall is forecasted today with strong south/southwest winds between 30-40 MPH with gusts expected 50-60 MPH. Even with this dense snow, sensitive wind slabs will be forming today and will become reactive. Wind slabs 1-2 feet deep are likely today at middle and upper elevations, especially on north and east-facing aspects.

    Additional Discussion: In wind-protected areas at middle and upper elevation you can expect to see sensitive storm slabs building today. 

    (12/21/2022)

    Observation submitted of a small wind slab avalanche north of Tamarack Resort about 7500' on an east aspect, about 100 wide, depth range 6" to 2'

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Persistent weak layers have been found at varying elevations and on multiple aspects throughout our advisory area. Underneath 30-45 cm (12-18") of snow a layer of buried surface hoar and near-surface facets has been producing unstable results in snowpits for nearly a week now. With rain at lower elevations and heavy snow at upper elevations, this weak layer will be undergoing tremendous strain today. Avalanches triggered on this persistent weak layer have the ability to propagate remotely and over long distances. 

    Additional Discussion: This persistent slab problem becomes complex today for a multitude of reasons:

    1.  With the rain level hovering around 6500 feet. If enough water penetrates the snowpack and lubricates this persistent weak layer, wet slab avalanches are possible below 7000 feet. Dry slab avalanches are likely above 7000 feet.
    2. If you've been reading our forecasts you know there has been another persistent weak layer near the ground we've been discussing since early December. If large enough avalanches occur within the upper snowpack there is the slight possibility for an avalanche to step down to a deep persistent avalanche near the bottom of the snowpack. Although unlikely, this scenario would be most likely to occur in areas where the snowpack is shallow (less than 3.5 feet deep).

    (12/26/2022) Photo: Studley

  • Loose Wet

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

    Rain has been falling at middle and lower elevations since yesterday. Temperatures were above freezing below 7000 feet for nearly 48 hours. These ingredients create the perfect recipe for wet loose avalanches. It is not springtime and wet loose avalanches are not confined to certain areas of the compass. You can expect to encounter wet loose avalanches on all aspects of the compass at middle and lower elevations.

    (12/26/2022)

    Wet loose snow coming off the rocks in steep terrain.

    Photo: Studley

Avalanche Discussion

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

Today's avalanche problems are complex and the avalanche problems are many. The mountains have undergone a severe weather transition within the past 48 hours. With complexity comes uncertainty. Yesterday, we observed a moist upper snowpack already showing signs of instability with wet loose avalanches. A warm and wet storm bringing moisture from as far away as Indonesia coupled with strong south/southwest winds will add tremendous stress to our changing snowpack. Rain falling at such high elevations is unusual for this time of year.  Unusual weather events can lead to unusual avalanche events. Today is not the day to go charging in the mountains. Allow the snowpack and the mountains to adjust to this weather change. Traveling in, around, or underneath avalanche terrain is not recommended today. The avalanche danger will be increasing throughout the day. 

 

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