Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Tue
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 in all zones of our advisory area. Warm temperatures and sunny skies will produce large and deadly avalanches. Avoid traveling in avalanche terrain today. 

Problemi valanghivi

  • Persistent Slabs

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

    Avoid traveling in avalanche terrain today. The likelihood of spontaneous large and very large avalanches makes steep terrain and avalanche runouts very dangerous. Heat and radiation are destabilizing hard slabs perched on deeply buried weak layers. These layers are widespread but variable in strength, making it impossible to determine which slopes will fail and when they will fail.

    Multiple large hard slab avalanches occurred the last 3 days in Glacier Park and the Flathead Range and likely failed on buried weak layers above an early February crust. Debris from these slides can run the full length of avalanche paths, making surviving one of these events nearly impossible. 

    (3/17/2024)

    This is a hard slab avalanche on Nyack Mountain that failed on a northeast aspect at upper elevations on March 16. This slide likely failed on a layer of facets above the early February crust. 

    Photo: Mark Dundas

  • Loose Wet

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

    Prolonged warming and no overnight refreeze are causing an increase in wet avalanche activity. Wet Loose and Wet Slab avalanches will occur on all aspects. 

    Mushy snow that does not support your weight or machine is a sign you could trigger a wet avalanche. Escaping a large wet avalanche is nearly impossible. Be aware of the terrain above you. In the past two days, wet avalanches large enough to bury a person have hit frequently used snowmobile trails. Avoid being on or under steep slopes.

    (3/17/2024)

    Wet debris covering the frequently traveled Canyon Creek road. Expect similar avalanches to occur today. Avoid traveling beneath steep slopes. 

    Photo: Lloyd Morsett

  • Cornices

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

    Impressive southwest winds built large cornices along alpine ridgelines in late February/early March. Intense warming this weekend may weaken these features. A failing cornice can send large blocks of snow trundling downhill, potentially triggering a destructive avalanche.

    The nature of this problem is highly unpredictable and should warrant your respect. Give these whales a wide berth above and below a corniced ridgeline to reduce your risk. Don’t get surprised by a cornice breaking further back than expected.

    (3/7/2024)

    A cornice fall in Rubideau Bowl in the Apgar Range just north of Apgar Lookout. This feature substantially  increased in size during the intense wind event of February 28 and 29. Cornices can fail spontaneously. 

    Photo: Mark Dundas

Avalanche Discussion

Since March 15th, reported avalanche activity favors sunnier aspects. Click on this for a visual. Large avalanches are failing as both slabs and point releases. Expect more widespread avalanche activity today due to warmer overnight and daytime temperatures. 

Amongst all of the recent natural avalanches, two noteworthy slides failed in the last 24 hours. The first (observation) is of a wet slide that put up to 10 feet of debris on the Canyon Creek road in the southern Whitefish Range. The avalanche failed naturally and came down to a heavily traveled route. Throughout the advisory area, expect to see more avalanches come down and bury frequently traveled routes. The second (observation) is of a Very Large (D3) avalanche on a northeast-facing aspect. This slope receives very little solar input. This may be the start of a pattern today where we see more avalanche activity on north-facing aspects.

Don't let a superficial crust at low elevations fool you into thinking that upper elevations refroze last night. A temperature inversion allowed valley floors to drop below freezing, while middle and upper-elevation stations averaged in the upper 30s. Last night was the warmest night yet, and we are going into the warmest day of the year. 

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