Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

We are not entirely out of the woods when it comes to triggering avalanches on persistent weak layers buried six to 18 inches below the surface - mostly on shady, sheltered slopes. Nor would I be surprised to see some wet loose avalanches from very steep, sun-baked terrain as temperatures climb above freezing. You reduce your chances of triggering a persistent slab by sticking to planar or concave slopes less than about 35 degrees. Pay attention to warming and be off, and not under, sunny slopes before the surface is slushy.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    On shaded and sheltered slopes without a thick, hard crust, it remains possible for you to trigger an avalanche that breaks on buried weak layers. While these layers are widespread across the forecast region, they have been gaining strength. The only avalanches breaking on these layers ran in the southern Whitefish Range. Steep, shaded, wind-sheltered slopes at mid and upper elevations give me the most lingering concern. You can still find dry snow while avoiding the problem. Stick to planar or concave slopes with clean runouts - no gullies, trees, or rocks below.

    (2/7/2022)

     A rider stomped along a cornice/rollover and set off a decent sized slide, 6-12" crown, approx 100' wide. North-northeast aspect, 6380 feet in the Southern Whitefish Range on 2/7 

    Photo: Public

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    If the sun thaws the surface crust and temperatures crest above freezing, watch for rollerballs as the first signs that wet loose avalanches are again becoming a hazard. Sunny slopes with shallow snow cover, and rocky or vegetated areas will warm first and most. Note wet snow sticking to your boards or machine. Sinking into wet snow above your boot top is also a warning sign. Confined terrain like chutes and gullies make wet debris hard to escape.

    (2/10/2022)

    Triggering rollers.

    Skyland/Marias Pass

    Photo: Clancy Nelson

Avalanche Discussion

Observations from Thursday focus on widespread rollerballs and a few wet loose avalanches (example 1, example 2, example 3). Few clouds and freezing temperatures overnight have likely resulted in a new melt-freeze crust up to at least 6500 feet on sunny aspects and all aspects at lower elevations. 

Strong winds earlier in the week have left old, hard wind slabs below leeward ridgelines. In some areas, these stretch well downslope. They have been gaining strength since the 7th, when a very large wind slab avalanche ran in Stanton Creek. Well-developed cornices hang over some typically leeward slopes. 

Skiers Thursday found dry, settled snow on shady, northerly slopes above about 6000 feet. A spotty rime crust dots the Flathead Range. 

A freezing rain crust covered all aspects and elevations around Whitefish Mountain Resort on Wednesday.

Persistent weak layers - surface hoar in the southern Whitefish Range and facets in the Flathead -  are buried six to 18 inches deep. The last reported avalanche failed on those weak layers on the 7th east of Whitefish Mountain Resort. The facets have not shown any signs of instability since blase experienced rumbling collapses in the northern Flathead on the 6th. The likelihood of triggering a slab on old, weak snow is diminishing. Warm temperatures are helping these layers stabilize, though the process is slow.

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