Lawinenlagebericht

Whitefish Range

Flathead Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Despite the sunshine, avalanche conditions remain dangerous as you gain elevation. You can trigger large and treacherous avalanches that fail under the most recent snow or on weak layers buried up to 4 feet deep. Avoid slopes steeper than about 30 degrees, especially where winds have drifted the new snow into denser slabs. Avoid slopes exposed to large avalanche paths overhead. 

Lawinenprobleme

  • Wind Slabs

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

    Slabs of drifted snow failed naturally in the northern Whitefish Range on Tuesday. 3 to 7 inches of new snow fell with strong westerly winds. Dense, textured slabs can fail at the new/old snow interface. They can crack around you and under your machine. Resist the lure of steep slopes today. Use caution near and below slopes in exposed leeward terrain: down-wind of corniced ridgelines and cross-loaded features like chutes and mid-slope convexities. Sheltered terrain with cohesionless snow and low slope angles is the safest choice. 

    Shooting cracks in drifted snow.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Surface hoar and facets are buried 2 to 4.5 feet deep atop the mid-January crust. They failed and resulted in large avalanches through Tuesday. They have also been responsible for a long streak of natural, and triggered avalanches - as well as several accidents and near misses. New snow and wind recently beefed up slabs atop these nagging headaches. Smaller avalanches may step down and trigger a very large and dangerous avalanche. Avoid exposure to the tracks and runnouts of large avalanche paths. Stick to slopes about 30 degrees or less. Slopes with a consistent slope angle, and no breakovers, are the safest choice to avoid the problem. 

    Hard slab failed on bruied facets.

Avalanche Discussion

US Highway 2 through John F. Stevens Canyon may be closed for several hours today due to avalanche mitigation.

On Monday and Tuesday, the most recent atmospheric river event brought a round of natural and human-triggered avalanches. Blase reported several slides that ran on drifted and cross-loaded slopes in the northern Whitefish Range. The majority of reported activity was focused on the southeastern corner of the forecast area, along the southern edge of Glacier Park. Most avalanches started above 5,500 to 6,000 feet. They were the result of heavy new snow and strong wind overloading the old snow surface or buried weak layers. Riders reported whumpfing collapses and cornice falls at middle and lower elevations from the same area. A large debris pile crossed the Going to the Sun Road and McDonald Creek in central Glacier Park. Cam triggered a wind slab on a cross-loaded feature in the Swan Range early in the storm. 

Freezing levels Monday hovered below 5,000 feet. Below that elevation, as the cold front passed, 1-6 inches of new snow fell on a rain-soaked snowpack. 5-17 inches fell on older, dry snow, wind-affected surfaces, and even surface hoar and small facets at middle and upper elevations. Moderate to strong westerly winds thickened and stiffened slabs throughout the storm. Snow continued to drift overnight. All that loading overburdened older problem layers. Weak surface hoar and facets are buried 2 to 4.5 feet deep atop the mid-January crust.  These deeper layers are not dormant. They were responsible for some of the most recent avalanche activity at middle and upper elevations. 

Pro Tip: Make a plan. Choose terrain and set limits before you leave the trailhead. Making decisions based on the avalanche forecast over breakfast can help temper powder fever once you're sitting at the top of that slope. Rule out the most dangerous slope angles, aspects, elevations, and terrain features before you go. Then follow your own guard rails for a safer backcountry experience. 

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