Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
3 · Erheblich
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Kernpunkte

An avalanche WARNING is in effect. Rain, heavy snow, and wind-transported snow are overloading a snowpack that has gone through a dramatic change over the last week. 5 to 14 inches of new snow today will increase the threat of human-triggered slab avalanches. These slabs will be thicker and more dangerous on the downwind side of ridges and gullies. A slab failing on weak snow near the ground  may run long distances and be unsurvivable. Avoid avalanche terrain today.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1–3

    Dropping temperatures and continued precipitation may bring 5 to 14 inches of new snow to the forecast region. New snow will form fresh slabs below roughly 6500 feet, and thicken existing slabs at upper elevations where recent precipitation has fallen as snow. There is uncertainty about where the rain/snow line exists. Expect new snow to be reactive to the weight of a rider or machine. Slabs will be thicker and more dangerous the higher you climb and in areas where winds have drifted snow. Shooting cracks under your board or machine are signs this problem exists. Stick to slopes with low slope angles to manage this problem today. 

    (12/26/2022)

    Slab avalanche that failed naturally on the 26th. 

    Photo: Adam Clark

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3.5

    Snow, rain, warm temperatures, and wind loading are stressing weak snow buried near the ground. Give avalanche terrain a wide margin for error today. Slides may break far distances and run down to the valley floor. The only way to manage this problem today is avoidance. That means staying out from under steep terrain and keeping your slope angles less than 30 degrees.

    (12/22/2022)

    The crown of this large natural avalanche wrapped across terrain features and through burned snags on an upper elevation, southeast facing slope. 

Avalanche Discussion

Since December 22nd, we’ve received over 3 inches of water and undergone a 70-80 degree Fahrenheit temperature swing throughout our forecast region. Talk about change! Precipitation has fallen as rain below roughly 6500 feet, with some reports of rain reaching 7000 feet. We’ve received observations of numerous wet snow avalanches that failed at lower and mid elevations, and a few dry slab avalanches failing at upper elevations (observation, observation, observation).

Thankfully temperatures are dropping below freezing and liquid is turning to snow. Precipitation totals will favor the Swan Range, where up to 14 inches may fall by tonight. The Whitefish Range may see the lower end of snow totals at around roughly 5 inches. Winds are forecasted to remain at speeds capable of transporting snow.

Due to high forecasted precipitation totals, we combined the problem Wind Slab with Storm Slab. If precipitation totals verify, expect to find soft storm slabs on all aspects. We suspect these will be more likely and widely distributed above 5000 feet due to the snowline dropping throughout the day. Winds have, and will continue to drift snow into cohesive slabs. Slabs of drifted snow will be thicker and more dangerous below ridgelines and in cross-loaded gullies further down the slope. Our travel advice today is simple, avoid avalanche terrain.

Remote weather stations at low elevations are just beginning to drop below freezing as of 6 AM this morning. Cooling temperatures will refreeze the snow surface and reduce the likelihood of wet snow avalanches. IF you head out and find no crust and wet snow beneath the new snow, assess and manage your terrain for wet snow avalanches. Yet again, that will be sticking to slopes with low slope angles. We left the danger rating at low elevations elevated to Considerable primarily for overhead hazard. 

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