Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
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

Watch for slabs of wind-drifted snow, if your travels take you into upper elevations near the Flathead crest. Choose windward aspects or terrain sheltered from recent southwesterly winds for safer options. Cracking around your board or machine is a sign you found the problem. Adjust your approach and change aspects.

Problemi valanghivi

  • Wind Slabs

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

    Wind speeds over the last 48 hours have significantly dropped along the divide. Mt. Aeneas, just across the resevoir in the Swan Range, continues to blow at speeds capable of transporting snow. Slabs of drifted snow may be more confined to ridgelines of the Flathead crest. Steer around pillowy-looking surfaces or dune-shaped drifts at upper elevations.

    (1/15/2023)

    Crown of a natural avalanche that failed in the last week. 

    Photo: Cam

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–1.5

    Watch for loose wet avalanches and manage your slope angle while traveling through middle elevations en route to higher terrain. Anywhere from 1 to 4 inches of snow fell throughout the forecast area yesterday (Sunday). My party was able to trigger small loose wet slides in the new snow at middle elevations. Wet snow avalanches today will likely be small in size, but problematic if you get caught above a terrain trap.

    (1/14/2023)

    Debris from a loose wet avalanche that piled up on a road cut. 

Avalanche Discussion

The current weather pattern will do little to change avalanche conditions from the past few days. Cloud cover, light wind speeds, and warm temperatures are keeping the snow surface from receiving a hard freeze. This, along with a few inches of new snow, keeps the threat of wet snow avalanches a problem. As daytime temperatures warm the snow surface, wet snow avalanches will be more common above the rain/snow line.

A buried layer of surface hoar is proving to be problematic in the Swan Range. It was buried on January 9th during a storm that favored the Swan Range with 1.2 inches of Snow Water Equivalent (SWE). On January 11th, an observer found it buried under 6 inches of snow and reactive in snowpit tests at 6000 feet. A snowmobiler remotely triggered a large slab avalanche below a ridgeline that same day (observation). Yesterday, my partner and I found evidence of natural slab avalanches that failed sometime in the last week. We remotely triggered two slabs while walking a ridgeline (observation). We were surprised at how sensitive this weak layer remained, a week after its burial. These are clear signs to avoid shaded aspects where winds drifted snow into thicker slabs, and that this problem may stick with us for a while.

Although slabs are failing on a persistent weak layer, we plan to list them as a Wind Slab problem for the next couple of days, as we collect more information. As of right now, we are more concerned about areas where there is enough snow to form a slab above this fragile weak layer. So far, that is where winds have drifted snow.  

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