Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Recent avalanches and whumpfing collapses are red stop lights telling us to stay off of slopes steeper than 35 degrees. North and east winds increased overnight and will continue to blow at speeds capable of transporting snow. Identify slabs of drifted snow and steer around them.

Problemi valanghivi

  • Persistent Slabs

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

    We received an observation of 2 large avalanches in the Swan Range that likely failed sometime in the last week. Sunday, avalanche mitigation work at Whitefish Mountain Resort produced avalanches that failed up to 2 feet thick. These avalanches and the long list of whumpfing collapses are bullseye information telling us to stay off of and out from beneath avalanche-prone terrain. Be wary of steep rollovers, road cuts, and the runouts of large avalanche paths above you. Enjoy powdery snow on lower-angled slopes.

    (12/6/2022)

    An 18" thick crown of a soft slab avalanche east of WMR. This slide failed on a faceted crust.

    Photo: Mark Dundas

  • Wind Slabs

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

    Watch out for slabs of drifted snow in unusual locations. Winds shifted to the north and east overnight and clocked speeds capable of transporting snow. These slabs may be reactive to the weight of a rider and grow large enough to injure a person by the end of the day. Pillowy-looking surfaces, active blowing snow, and shooting cracks are signs to seek out wind-protected slopes.

    (12/9/2022) 30 cm fresh wind slab - skier triggered intentionally while ski cutting

Avalanche Discussion

The most recent change you'll see today is wind drifting snow onto aspects that face south through the west. Overnight, wind stations in all three forecast areas averaged speeds from 12 to 23 mph out of the east and north. This pattern will continue throughout the day today. Expect to find slabs of drifted snow in areas that were previously sheltered from the wind. Look for clues of blowing snow and dune-shaped pillows for locations to avoid. Higher quality and safer riding conditions will be on slopes sheltered from the wind.

The saga continues. Observations of loud whumpfing collapses continue to dominate the observations page. Don't allow impatience and message fatigue to creep into your mind and influence your decisions to step out into steeper terrain. One group on Sunday observed two large avalanches with crowns up to 3 feet deep in the Swan Range. Our best guess is that this happened sometime in the past week. On Saturday, a group in the Apgars triggered a collapse that shook trees 200 feet away. That is enough evidence in the past 48 hours to continue to stress the importance of slope angle and terrain management. Manage your slope angle by sticking to slopes less than 35 degrees or closer to 30 degrees if you want to build a wider margin of error. I will still avoid walking in the runouts of large avalanche paths and steer around steep breakovers. Fortunately, there is still plenty of quality riding on lower angles slopes sheltered from the wind.

A huge thank you to all the people submitting observations so far this season. 

Education - Our next Avalanche Awareness presentations are Tuesday, December 13, at Whistling Andy Distillery, Bigfork, and on Wednesday, December 14, at Penco Power Products, Kalispell. You can get more details about these free events on our events calendar.

Observations - Thanks to everyone who's been utilizing our new observation submission page. Try it out and help your community by sharing what you see in the backcountry. The form requires you to fill out the location fields and put a dot on a map. Be as specific or vague as you want. Our new Observation View page highlights signs of instability and allows you to filter by date or zone to pull out reports relevant to your objectives.

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