Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You are less likely to trigger an avalanche where the snow surface is frozen and supportable. Avoid steep slopes peppered with rocks for an added margin of safety. Falling cornice and small surface slides can trigger destructive avalanches on buried weak layers. Don't linger below cornices or sun-baked slopes during the hottest part of the day. 

The danger may be greater in the Northern Whitefish Range (Ten Lakes), which received more recent snow. Riders traveling in this area may trigger small avalanches in wet or wind-drifted snow. 

Problemi valanghivi

  • Persistent Slabs

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

    It is becoming increasingly difficult to trigger large avalanches on buried weak layers. Loading and wetting of these layers produced a natural cycle of large avalanches during last week's rain. 

    The January Drought Layer (JDL) may remain intact on upper-elevation slopes that received lesser amounts of rain. This appears to be more common in the central and southern Whitefish Range and northern Swan Range. I would be leery of any steep slopes that do not have a thick and supportable crust near the surface. 

    Riders are most likely to trigger large avalanches where weak layers are closest to the surface (i.e. rocky or wind-raked slopes). Elsewhere, cornice and small surface slides can still apply sufficient force to initiate a fracture. The resulting avalanche could break thousands of feet wide and up to 8+ feet deep. A rider is unlikely to survive such a slide. 

    (3/23/2026)

    Steep and rocky alpine slopes with cornice looming overhead: That is where you are most likely to tangle with large avalanches on buried weak layers.

    Photo: Flathead Avalanche Center

Avalanche Discussion

You might have noticed that we've moved back and forth between the Wet Slab and Persistent Slab problems several times during the last week. This transition occurs as we hedge our bets on where liquid water might be in the snowpack and what effects it could have on weak layers. Regardless of the problem, the outcome is the same: large avalanches on buried weak layers are possible. 

After 24+ hours of cold temperatures, I’m betting that meltwater will not be the primary cause of any large avalanches today. A more likely scenario is that weak layers are triggered by a falling cornice, small surface slide, or— to a lesser extent—a rider. We have trimmed this problem to elevations above 6500’, with the expectation that lower slopes have been worked over. 

Today’s uncertainty is driven by variable weather across the advisory area and limited observations. The northern Whitefish Range is one clear outlier, as the Stahl Peak Snotel recorded 1 inch of SWE Tuesday night. You are more likely to find lingering wind slab or wet snow problems in any locations favored by recent snow.

 

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