Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Saturday's storm affected the FlatheadRange and Glacier Park with varying intensity, creating dangerous avalanche conditions in areas favored by snowfall. Expect to find fresh, thick slabs reactive to a rider's or their machine's weight. Slabs may be triggered from a distance and propagate surprisingly far. Carefully evaluate any steep slopes loaded by eight or more inches of new snow. 

 

Problemi valanghivi

  • Storm Slabs

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

    Heavy, dense snow and moderate to strong southwest winds formed fresh slabs overnight. On shaded aspects, these may rest on weak surface hoar or faceted snow, making them more sensitive to triggering than expected.  On slopes open to the sun, they may rest on a slick faceted crust, inhibiting bonding. Slabs will be thicker and more dangerous downwind of ridgelines and saddles.

    Monitor the depth and density of the fresh snow you travel through. Utilize hand pits and test slopes to observe how well the snow adheres to the underlying layer. Cracking in the snow surface is a sign that the slab you are on is unstable, directing you to lower-angle terrain free of overhead hazards. 

    (4/7/2024)

    This avalanche failed in the storm snow and is a soft slab avalanche. This type of slide could occur with a storm slab problem.

    Photo: Jeff Metsky

  • Loose Dry

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

    Areas that received six or more inches of fresh snow will be most at risk for loose snow slides. The new snow that fell on solar aspects rests on a slick crust, which allows triggered slides to travel farther than expected. On shaded slopes, the new snow rests on weak surface snow, inhibiting strengthening and allowing slides to entrain snow and grow larger.

    Mitigate this problem by managing your sluff. Be wary of long-running gullies where sluffs can entrain substantial snow and sweep you off your feet. Limit time spent above terrain traps where debris can pile up deep. 

     

    (11/7/2024)

    Multiple loose snow slides in the Peter's Ridge area of the Swan Front. These are located in the mid-elevation band and are on southwest and south aspects. This area experienced heavy snowfall two days before this photo was taken. 

    Photo: Keith Hammer

Avalanche Discussion

Feast or famine. Saturday's storm was unusual in its distribution. The northern Whitefish Range was walloped with an impressive 2.6 inches of SWE (Snow Water Equivalent) and a foot of settled snow, while the WMR ski area in the southern part of the range picked up a half inch of water and 4 inches of snow. The typically soggy Noisy Basin in the Swan Range picked up a measly inch or two. Uncertainty lies with the Flathead Range and southern Glacier Park, where an inch of water fell, but snow stations only show up to 5" of new snow. We assume that upper elevations may have ten or more inches of fresh snow. Moderate to strong winds blew overnight, redistributing this snow.

Dangerous avalanche conditions formed in the northern Whitefish Range, central and southern Glacier, and the Flathead Range due to the copious moisture and wind. Due to the impressive precipitation intensity, we assume there was a natural avalanche cycle overnight in the northern Whitefish. Natural avalanche activity could occur today due to the ongoing wind loading. Above treeline, a human-triggered avalanche is likely today in areas that received eight or more inches of new snow. We recommend staying off of and out from under any loaded steep slopes at upper elevations. 

Did you hear about the app? You can now access our region's forecasts, observations, and weather data directly from the Avy App (IOS; Android). Many features are accessible offline, so you can win debates about the avalanche problems right in the backcountry or submit an obs while driving home. 

Registration is open for this season's avalanche courses. Get some learning done!  There's an Avalanche Awareness class on Wednesday, December 11th, at 6:00 pm at the Stonefly Lounge in Coram.

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