Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

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

Pay attention to today's wind and snowfall. Cracking around your feet or machine means you can trigger an avalanche in wind drifted snow. It is unlikely, but not impossible to trigger a large avalanche on buried weak layers. Choose slopes with clean run-outs - free from exposed rocks, cliffs, trees and gullies - to improve the outcome of any slide. 

Problemi valanghivi

  • Wind Slabs

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

    You can find thin slabs of wind-drifted snow in unusual locations. Wind direction varied from northeast to southwest during the last 24 hours. Northeasterly winds peaked last night as snowfall set in across the advisory area. 

    Look for signs of wind-affected snow downwind from ridges, saddles or other prominent terrain features. Scalloped surfaces or dune-shaped features are hints that the wind has been sufficient to transport snow.  Cracking around your feet or machine means you have found an unstable slab and suggests you seek out less steep or more wind sheltered slopes. 

     

    (12/27/2024)

    Ripples on the snow surface signify that the wind has been at work. Today, you might find wind-affect surfaces in unusual locations.

    Photo: Mark Dundas

  • Persistent Slabs

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

    You are most likely to trigger a slide where the weak layer is closer to the surface. This includes rocky or wind-scoured slopes and convex rollovers. Choose planar slopes with a deep and uniform snowpack to decrease your chances of triggering a slide on buried weak layers. Although the likelihood is low, the resulting avalanche could be very large and difficult to escape. 

    Several layers of facets or faceted crusts have been observed in the top three feet of the snowpack. These have been found on a variety of aspects.  Signs of instability have tapered off rapidly following last-weekend's storm. 

    The well-documented 12/7 surface hoar layer is still easy to find in some pits.  However, this layer appears to be gaining strength as the surface hoar breaks down (obs).

     

    (12/24/2024)

    These large avalanches were triggered by cornice fall and likely failed on a buried weak layer. It is becoming increasingly difficult to trigger an avalanche on these layers. However, the resulting avalanche would be large and difficult to escape. 

    Photo: Michael Reavis

Avalanche Discussion

If you can’t tell, we’ve recently been a little on edge regarding wind. With abundant snow available for transport, it doesn't take much wind to build sensitive drifts on leeward slopes. Yesterday (Friday), on my drive into Hungry Horse, northeast winds were already ripping through Bad Rock Canyon and drifting snow across Highway 2.  The drifting was more extreme on my drive home. It's been a while since we’ve seen northeast winds in our area. Take some time to refamiliarize yourself with a couple of quirks.

  • Northeast winds are channeled through JFS Canyon and along HWY 2. They can rake mid- and low-elevation slopes, forming wind drifts much lower than you might expect and on atypical aspects.
  • The south face of Whitefish Mountain Resort can be hit hard by easterly winds. Today’s snow report reads, “Please be mindful of wind drifts as you make your way around the mountain.”
  • The west slope of the Swan Range is another area that tends to take a beating during periods of easterly winds. This event wasn’t particularly strong, so the effects may be less there.
  • In general, don’t be surprised if you find wind-drifted snow on various aspects and elevations today. 

Most observations from yesterday noted some minor loose dry activity while riding steep slopes.  Sluffing will likely continue today in sheltered areas.  Keep in mind these small slides can push you off your line and through the bushes, over a cliff, or into the creek.

Downloaded the app yet? 

You can now access our region's forecasts, observations, and weather data directly from the Avy App (IOS; Android). Many features are accessible offline, so you can doublecheck danger ratings and travel advice on the drive to the trailhead or in the backcountry. 

Events and Education:

Want to start your New Year on the right foot? Sign up for the Avalanche Awareness class on January 6th. Check out our calendar for other upcoming events. 

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