Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 8 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Dangerous avalanche conditions build today with the passage of a significant cold front. The hazard will rise throughout the day as high winds and heavy snowfall construct fresh slabs. Localized areas that receive more than 6 inches of snow will harbor a greater hazard as slabs increase in depth. Stay off of and out from under slopes where you notice recent wind loading.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    Widespread high winds, combined with 7-12 inches of fresh snow will form slabs on upper elevation, leeward slopes and cross-loaded gullies. Southwest winds will be strong enough throughout the day to rapidly transport this snow into thick, hard slabs. How deep and hard these slabs are will depend on which range you are in. The Flathead and Whitefish Ranges will be favored for snowfall, and thus wind slab development. The Swan may have less snow available for transport, and thus less widespread and smaller slabs

    On many slopes, the new snow will rest atop a stout melt freeze crust from last week’s Atmospheric River event. In areas that are very protected from the wind, you may find more than 8 inches of new snow. If you’re lucky enough to find these protected zones, steer clear of steep, convex terrain and manage for a Storm Slab avalanche problem.

    Be cautious about crossing avalanche runouts today (Wednesday). Large avalanches could release naturally high above you and travel far downslope. The lowest risk will be in areas free from wind loading, so travel on scoured slopes. Let your route take you from one hard crust surface to another. 

    Wind-loaded, leeward slopes will be possible for a human  to trigger avalanches on today. A slick bed surface likely exists under any new wind slab. Respect this fresh hazard and travel from one scoured slope to another in order to find safety. 

    Photo: Michael Reavis

Avalanche Discussion

Button up and hang on. Today’s storm will bring the much-desired and needed snow. The new snow will bring a partner to the dance, though: wind. Moderate to strong southwesterly winds with gusts of 60-70 mph will be widespread in the upper elevations. Falling trees may be a hazard, making travel to areas where the fresh snow has accumulated hazardous in its own right.

Today’s new and drifted snow will fall on a variety of old snow surfaces. Depending on your elevation, you may encounter wind-scoured crusts, supportable and refrozen crusts, or moist, unsupportable mush, maybe topped with breakable crust. On Monday Cam and I traveled to 7,000 feet in the Flathead range. At that elevation we were able to easily travel on a scoured, ridgeline crust and expect that it continued if we had gained elevation. Sunday’s observation from Glacier National Park reported a “glassy” surface to the crust on all aspects above 6,000 feet. 

With the winds forecast for today, much of the fresh snow will be rapidly transported onto leeward slopes and crossloaded onto gully walls. The more intense the snowfall rates are, the more intense the loading will be. Upper-elevation lee and cross-loaded slopes will quickly accumulate slabs of wind-affected snow this afternoon.

Wind, new snow, unexplored crusts and abnormal weather conditions will make for a dynamic experience in the mountains today.  

Friends of the Flathead Avalanche Center is hosting a Ladies Rescue Clinic this Saturday the 20th. There are still a few spots available, register online.

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