Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

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

An Avalanche Warning is in effect. 1 to 3 feet of new and drifted snow, rain-on-snow, and warm temperatures are keeping the avalanche hazard elevated. Avoid being on or under slopes steeper than 30 degrees. Avalanches may run long distances and will be large enough to bury, injure, and kill a person.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    Stay off of and out from underneath slopes 30 degrees or steeper. On Monday, Mark found touchy avalanche conditions with soft slabs failing a foot thick and propagating up to 40 feet wide. Today, expect slabs to be reactive to the weight of a person or machine and large enough to bury, injure, and kill a person. Slabs will be thicker and more dangerous the higher you climb, and on the leeward side of ridges and gullies where winds drifted new snow. Any triggered slabs of dry snow may run surprisingly far distances and be more destructive if they entrain the wet snow below.

    (2/28/2022)

    A soft slab intentionally triggered in the southern Whitefish Range. Additional snow has fallen since the event, making the potential size of triggered slides larger. 

    Photo: Dundas

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–3

    Avoid being on or under steep slopes today. Freezing levels climbed to roughly 6500 feet and are forecast to stay there for the remainder of the day. Rain will continue to wet the snow surface, causing avalanches to fail naturally. Wet debris can run long distances and be very destructive.

    Wet debris may run long distances and through the not-so-obvious kind of avalanche terrain. This photo was taken last season after a rain on snow event.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3.5

    Rapid loading of the snowpack may cause weak layers deeper in the snowpack to fail. If triggered, slides will propagate wide distances and be difficult to survive. Avoid being on or under slopes 30 degrees or steeper. Allow the snowpack time to adjust after the wallop it received in the past 36 hours.

    (2/8/2022)

    Very large (D3) avalanche that likely failed on buried persistent weak layers on 2/6 or 2/7. It is possible that rapid loading and rain may cause this layer to fail. 

    Photo: Alan Davis

Avalanche Discussion

A whopping 3 to 3.6 inches of water fell in the past 36 hours throughout the forecast area. Remote weather stations are reporting roughly 10 to 20 inches of new snow at middle and upper elevations. Temperatures and the snowline remained lower than forecasted during the day on Monday, keeping the snow level to around 5000 feet.  Temperatures climbed above freezing at stations around 6000 feet last night.

An additional .5 to 1.5 inches of water is forecasted to fall today with freezing levels at, or just above 6500 feet. Triggered slabs of dry snow at upper elevations, or wet avalanches at middle elevations will entrain wet snow and run long distances down into low elevations. Debris may travel through timbered slopes and run into flat terrain. Do not find yourself standing in the runout of large avalanche paths and don’t allow vegetation to give you a false sense of security. Managing your slope angle is your only tool for a safe day. If you go out, plan your day strategically to stay on ridgelines and not expose yourself to slopes steeper than 30 degrees. 

3 inches of water is a common threshold to use for when avalanches may fail deeper in the snowpack. This threshold is true for incremental loading events that occur over a few days. Many remote stations throughout the forecast area show 3 to 3.6 inches of water in a 36-hour timeframe, and more is on the way. That is an IMPRESSIVE load in a short timeframe. This rapid load may cause very large avalanches to fail on layers beneath the new and old storm interface. We think the likely culprit will be avalanches failing on mid-January faceted crusts breaking a few feet below new snow. Weird weather can cause weird avalanches. 

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