Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Up to 6 inches of snow fell overnight, with a possibility of 10 more inches by tomorrow morning. If this weather forecast hold true, expect dangerous avalanche conditions to develop. Soft slabs will be reactive to the weight of a rider and may grow large enough to bury and injure a human. Stick to slopes less than 35 degrees if you see shooting cracks or more than 8 inches of new snow.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Expect soft slabs to form on all aspects as more snow piles up throughout the day. These slabs will be thicker and more dangerous in areas where the wind is transporting new snow onto the leeward side of ridges and gullies. Look for signs of shooting cracks and listen for whumpfing collapses. Today, manage the problem by sticking to ridgelines and riding in terrain with slope angles less than 35 degrees. Manage your overhead hazard by avoiding traveling under large avalanche paths.

    (1/29/2022)

    Shooting cracks away from your boards or machine is a sign you've found a slab avalanche problem. 

    Photo: Clancy Nelson

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–3

    Weak snow near the ground failed in a handful of large avalanches initiated by a wet, warm storm on January 12. No recent avalanches, benign weather, and snowpit tests show that this layer is gaining strength and is unlikely to propagate. New snow today will not likely deliver enough load for this to be a concern. This problem exists in start zones above 8000 feet and is a low probability, high consequence scenario.

    (1/24/2022)

    Performing instability tests on weak layers near the ground.  Results show this layer is unlikely to propagate.

    Photo: Cam Johnson

Avalanche Discussion

Overnight snow totals favored the Flathead Range and Glacier National Park. The remote weather station at Tunnel Ridge in the Flathead Range is winning the race as of 7 AM this morning with 6 inches of new snow. Stahl and Whitefish Mountain in the Whitefish Range are showing 2 to 3 inches, where Noisy Basin in the Swan Range got skunked with no measurable precipitation overnight.

Today's avalanche forecast relies heavily on today's precipitation forecast. We have higher confidence that dangerous conditions will develop in the Flathead Range where an additional 10 inches of snow may fall by tomorrow morning. The Whitefish and Swan Range may see anywhere from 4 to 10 inches by tomorrow morning.

New snow is landing on a variety of weak surfaces. Crusts and wind-hardened surfaces dominate upper elevations, which will act as a smooth layer for new snow to slide on. In locations sheltered from the wind at all elevations, surfaces consist of surface hoar and/or faceted snow. These areas, which we've been pointing to for most of the season for safer riding, will be prone to avalanching if we receive 8 or more inches. Look at terrain with a fresh lens today since we have yet to deal with snow landing on surface hoar this season. If you see cracking around your skis, boards, or machine, you've found a slab. Heavy precipitation rates or 8 plus inches of snow is your cue to stick to slopes less than 35 degrees.

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