Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Roughly 5 to 7 inches of new snow has fallen in parts of the Whitefish Range and the Swan Range in the past 48 hours. You will mostly have to deal with this new snow hazard on wind drifted areas, or in steep chutes where a small avalanche can entrain enough snow to bury and injure you. If conditions point you towards steeper terrain, ride one at a time and position yourself where you can see your partner.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Overnight, winds have shifted from west to north and are reaching speeds capable of transporting new snow. Watch for slabs of drifted snow on varying aspects and on atypical features. Expect them to be thicker and more dangerous in areas where you find 6 or more inches of freshly fallen snow. The most enjoyable and safe riding will be in areas sheltered from the wind.

    (1/2/2022)

    The crown of a large slab avalanche is visible on the headwall of the Flathead Crest. This avalanche would likely be unsurvivable due to the size of the slide and the exposed rocks in the avalanche path. 

    Photo: Michael Reavis

Avalanche Discussion

More snow then expected fell overnight. Remote weather stations in John F. Stevens Canyon (southern Glacier National Park) are showing 4 to 11 inches of new snow in the past 12 hours. Yet 11 miles northwest, the Tunnel Ridge station is showing only 2 to 4 inches of new snow overnight. The difference highlights that storm totals vary greatly from basin to basin. Further west, the Whitefish Range and the Swan Range picked up 4 to 6 inches of new snow overnight.

The new, low-density snow is resting on faceted grains from last week's dry spell and cold temperatures. I would expect it to sluff easily and be slabby in areas where 8 or more inches of new snow have accumulated, or on terrain features effected by the wind, which shifted directions from west to north and east overnight. This shift may have drifted snow onto atypical features.

Your main objective today will be managing new snow hazards that will vary from drainage to drainage. Keep track of new snow depths as you move through terrain, and adjust your route on the fly. Be wary of steep slopes and avoid wind-loaded terrain features if you decide to seek out deeper snow in the Flathead Range and Glacier National Park, where 48-hour snow totals have reached 15 inches in favored locations. Test new snow by digging hand pits and utilizing steep, small terrain features before stepping out into bigger terrain.  

On Monday, Mark observed cracking and small slabs of drifted snow on Mt. Brown near Lake McDonald (observation). Since then, more snow has fallen and slabs have grown thicker. On Tuesday, an observer near Essex found 5 to 6 inches of new snow and had non propating results at weak interface roughly 8 inches below the surface (observation). In the Whitefish Range, observers found stubborn to unreactive wind drifted snow and no other signs of instability (observation, observation). 

Be prepared for cold weather. Travel with a partner and carry extra warm layers today.

Looking forward, a winter storm watch is in effect from Thursday to Saturday. Moderate to heavy snowfall rates are expected. Be sure to check back in on changing avalanche conditions.

Regioni coperte