Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

An Avalanche Warning is in effect. New snow and powerful winds have created widespread areas of unstable snow. Natural and human-triggered slides will be large enough to bury, injure, and kill someone. Avoid traveling on and beneath steep slopes. 

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–3

    Over the past 48 hours, intense precipitation rates formed slabs large enough to bury a person. On Sunday, two experienced riders were caught and carried in fresh slabs of drifted snow. Expect to find dangerous conditions in all aspects above 5000 feet. Reduce your chances of getting caught in a large slide by sticking to slopes less than 30 degrees and free of overhead hazards. There is excellent and safe riding on low-angled slopes.

    Winds from varying directions will drift snow into thicker slabs on the downwind side of ridgelines, beneath saddles, and cross-load the sidewalls of gullies further downslope. Pay close attention to drifting snow since east winds will begin to load slopes in unusual ways. A rippled surface and dune-shaped pillows are visual clues of a wind slab. 

    (2/20/2023)

    The crown of a large avalanche on a wind-loaded upper elevation slope.

    Photo: sw

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Buried layers of weak snow are being put to the test. Rapid loading can cause these layers to fail, creating a large deadly avalanche. If triggered, slabs can propagate wide distances, wrap around terrain features, and be large enough to bury, injure, and kill a person. A triggered storm slab or wind slab may step down to a buried weak layer, causing a destructive avalanche. The only way to manage this problem today is through effective terrain management - avoid traveling on and below steep slopes.

    (2/12/2023)

    This hard slab slid ontop of a faceted crust from late december. Slides today can break surprisingly wide and wrap around rock bands and other terrain features. 

    Photo: Burket Kniveton

Avalanche Discussion

We have an Avalanche Warning in effect for all three forecast zones. Today is a day to avoid all avalanche terrain. There is plenty of excellent riding on low-angled slopes not connected to steeper terrain above. Natural avalanches may run far distances and entrain a dangerous amount of snow. 

The faucet turned on yesterday (Monday) afternoon, and remote weather stations continue to pick up precipitation as of 6 AM this morning. Snow is forecasted to stop early this afternoon as arctic air grasps its frigid fingers around northwest Montana. Although precipitation rates will decrease, east and north winds will redistribute snow into firm slabs. These slabs will get formed onto slopes that don't typically get loaded by wind, which may catch you by surprise. Regardless of where winds are drifting snow, the travel advice is to avoid traveling in avalanche terrain. 

Storm Total Snow Water Equivalent:Stahl (Northern Whitefish Range): 2.5 inches.WMR (Sothern Whitefish Range): 1.5 inches.Noisy (Swan Range): 4.9 inches. Flattop (Glacier National Park): 3 inches. 

Mixed precipitation and rain on snow occurred at low elevations last night. This adds complexity to travel early this morning. Avoid traveling in steep terrain at low elevations if the snowpack is still saturated. Cold air will refreeze this surface later this morning, thus reducing the likelihood of loose wet avalanches. 

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