Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Snowfall overnight and today is creating new snow avalanche hazards on steep slopes at mid and upper elevations. While accumulations vary and forecasts are conflicting, you can trigger soft slabs that can be dangerous where there's more than about 8 inches of new and drifted snow. Signs of danger include shooting cracks and recent avalanches. Be alert for unexpected and changing conditions. 

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Snowfall overnight and today is creating new snow hazards. The primary threat is soft slabs that break in the new snow, or at the interface with the old snow. These will be most sensitive to a rider where they've been thickened and stiffened by winds. Expect more widespread hazards are you gain elevation and at the tops of chutes and leeward slopes. High snowfall rates and rapid settlement today mean slabs could become more sensitive through the day. 

    Pay close attention to new snow depths and signs of instability today. You can probe with your pole, look behind you at how deep your sled is trenching, and test the snow on short, inconsequential slopes. Shooting cracks and small slabs are clear signs that you can trigger dangerous slabs on larger, steeper slopes where there's more than about 8 inches of new snow. 

    (3/13/2025)The derbis from a shallow soft slab avalanche in the sidecountry of WMR. A good example of the size of slides you might encounter this morning, with larger slides possible later. The trees remain terran traps regardless. 

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    This afternoon's forecasted weather - temps above freezing and broken skies - may rapidly warm the surface snow and create localized wet snow avalanche hazards. Signs that this process is underway include clumps of snow falling from trees and rocks and rollerballs fanning downslope. Snow glopping onto your skins is another.

    On isolated slopes, the rollerballs may entrain enough snow to be dangerous. These slopes will generally be very steep, get direct sun, and be above terrain traps. Terrain traps include tree wells, which have expanded over the past week's settlement. And there are a lot of tree wells in the sidecountry of WMR. 

    Plan your day so you're off of and out from under terrain where these conditions are likely to develop this afternoon. Keep an eye on steep, rocky slopes above you, and move to shaded and less steep slopes as the day progresses. 

    (2/21/2025)

    Debris from a loose wet snow avalanche that is a good example of what you can expect today. 2/21, Whitefish Range, mid elevations.

    Photo: John Sullivan

Avalanche Discussion

A foot of new snow overnight - April Fools! Actually, no. At least a foot has accumulated in parts of the region - the big winners are the Ten Lakes area in the northern Whitefish Range, and Noisy Basin and Six Mile in the Swan Range. The Flathead Range so far appears skunked, with only 2 to 3 inches at mid elevations. The snow fell at over two inches an hour at times. There's not been much wind accompanying the snowfall. The exception is Link Mountain, where hourly averages have been in the mid teens overnight. 

Weather models seem to be struggling to depict this system. Accumulations have already exceeded some forecasts, and the numbers for today are inconsistent between models. The broad brush is that snowfall will taper off through the day, with some breaks in the clouds and temperatures nudging or exceeding freezing at mid elevations. Winds look to remain below tranport thresholds. If the forecasts are accurate, the Swan Range may pick up another 6 to 10 inches today, while the Flathead and Whitefish Ranges get about half that. 

So we have new snow avalanches hazards involving the snow that sits above Monday's melt-freeze or wet snow. While I expect the bond there to be good, we could see slabs breaking in the new snow. they could become more sensitive through the day, particularly if snowfall rates remain high. But also because of rapid settlement, with mild temperatures and short periods of direct sun. Be willing to get more conservative as the day progresses, and have an exit plan that avoids overhead hazards.

Some wet snow hazards may develop this afternoon. Dangerous sluffs will be isolated except in the Swan Range, where there's plenty of snow for sluffs to entrain. 

Mike and I saw the crowns of several very large, recent avalanches in the Skyland area Monday. These probably released midweek, when temperatures in the area climbed over 50 degrees. The crowns looked to be 1 to 2 meters deep, suggesting the slides failed on the January weak layers. Full obs here. 

Wanna help your crew stay safe? Eastern Oregon University is conducting a survey to better understand avalanche safety preparedness among motorized backcountry users. The survey will help us learn more about who is purchasing and practicing with avalanche rescue gear (beacon, probe, shovel) and participating in avalanche education—and why some riders are not. The survey is confidential and anonymous. Your feedback is invaluable in improving avalanche education and awareness. Please take a moment to share your experience and help us make a difference:

https://eoustmhs.qualtrics.com/jfe/form/SV_3L8QKAuZzcxJBLo

 

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