Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The danger will rise as solar radiation and high freezing levels wet recent storm snow. Triggered and natural wet snow avalanches will become likely and can be dangerous where there's more than about 8 inches of wet snow at the snow surface. Recently deposited slabs of drifted snow remain sensitive to a rider's weight. The chances of falling cornices will increase. Avoid traveling on or under steep slopes receiving sustained sun, particularly those capped by brows of overhanging snow. 

Problemi valanghivi

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    As the day progresses and snow warms at the highest elevations, cornices will weaken, and the chances of chunks calving off rise. Check above you for brows of snow cantilevered above steep start zones. Don't dawdle under these. If you're out late in the day, it would be prudent to avoid traveling under them altogether. If your traveling on a ridge, stay well away from the leeward side, because cornice chunks can snap surprisingly far back from their edges.

    (4/6/2022)

    A chunk of falling cornice triggered a slab of drifted snow on the slope below.

    Photo: Adam Clark

  • Loose Wet

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

    Snow sticking to your board, skins, or snowmachine is a sign that the snow surface is warming and getting wet. Rollerballs that release from rocks and trees and fan out as they tumble downslope are indicators that the wet snow is becoming unstable. Head for shady slopes with cold snow, or low-angled slopes that aren't below steep start zones. Triggered and natural wet loose avalanches can be large enough to be dangerous where there's more than about 8 inches of recent snow that's getting wet, and on slopes with continuously steep pitches. The heavy debris is difficult to escape, so avoid slopes steeper than about 38 degrees above terrain traps. 

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2.5

    You can still trigger slabs of drifted snow in chutes, couloirs, gullies and other terrain top-loaded or cross-loaded by recent winds. Clues to these conditions include dunes and lens-shaped drifts of wind-blown snow and hard, wind-packed snow surfaces. Collapses and shooting cracks are red-light signs that they remain unstable. The absence of these clues doesn't equal stability, so dig and test the bond between drifted snow and older, softer snow or crusts before committing to consequential terrain. The sensitivity of these slabs may change during the day, as their surfaces wet, so assess each slope with new eyes.

    (4/6/2022)

    A small slide released by a slope cut broke on weak snow at the early April melt-freeze crust. Slabs like this like remain sensitive to a rider's weight today.

    Photo: Cam Johnson

Avalanche Discussion

With mostly sunny skies and freezing levels spiking to about 10000 feet today, the snow on all but the coldest slopes will get moist or wet today. As it does, the likelihood of triggering wet loose avalanches will rise.  Initially, these will involve only the top few inches of recent snow. As the day progresses, they'll entrain more of the 4 to 20 inches of snow that sits above the early April melt-freeze crust. You're most likely to trigger them on shaded slopes where the sun didn't reach the surface snow and wet it Wednesday. At mid-elevations, that's slopes that face northwest through north to east at mid. At upper elevations, that's nearly all aspects, because Wednesday's sun wasn't enough to wet snow on sunny slopes. The hazard might vary in short distances, because strong winds early this week scoured and drifted snow on many slopes, particulary on windward terrain. Triggered and natural loose wet slides will entrain the most snow and be more dangerous on slopes with long, continuous pitches over 35 degrees. 

We continued receiving reports of recent or newly-triggered avalanches Wednesday. Cam triggered several small, soft slabs in steep terrain east of Whitefish Mountain Resort; most broke less than 8 inches deep and involved the most recent snow. He did trigger one pocket of harder drifted snow that broke on the early April melt-freeze crust. A rider near Essex reported drifting on both sunny and shaded sides of a ridge, with hand pits breaking at or above the early-April melt-freeze crust. A rider in the Skyland area reported two recent natural avalanches, one triggered by a falling cornice. I'm not sure how the rising temperatures will affect these slabs. I suspect they'll be most sensitive to a rider's weight as the slabs consolidate and their surfaces get wet. They might get smaller as the slabs wet through, and it's harder for cracks to propagate long distances. I suspect some denser, harder slabs remain sensitive to a person's weight today where they rest on thin layers of facets above the early-April crust. The only way to identify these is digging and testing, unless you see shooting cracks and hear collapses. 

Sunday, April 10 marks the last daily avalanche forecast for the season. We'll continue to issue conditions updates as needed into early May. Expect these at least twice a week, though we'll publish more frequently if conditions warrant. We'll post these in the afternoons.

Regioni coperte