Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sat
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Fresh snowfall and wind have increased the avalanche danger. Riders may encounter slabs reactive to their weight in both wind-affected and sheltered areas. Expect to trigger loose snow slides on many steep slopes. Enjoy today's powder on lower-angle terrain so you can do the same tomorrow.

The hazard is highest in the Swan Range, where more snow fell.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Overnight,  up to 6+ inches of snow was recorded in the Flathead Range and southern Glacier Park. Snow fell on a crust on southerly aspects and weak snow on northerlies, adding to the instability. Expect to find slabs both where the wind has drifted the snow and in sheltered locations. Slabs will be thicker and larger at upper elevations downwind of ridgelines and saddles and on the sidewalls of gullies. 

    Cracking beneath you or your machine indicates a sensitive slab directing you to lower-angle terrain. Utilize hand pits and small test slopes to assess how the new snow is bonding to the older snow surface.

    (2/24/2023)

    This is an example of a soft slab avalanche in a sheltered location on a convexity. You may encounter this problem today.

    Photo: Mark Dundas

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Yesterday, riders triggered sluffing on steep, northerly aspects holding 4-8 inches of weak snow. Snowfall overnight will increase the size of these slides and expand this problem onto southerly slopes, where the snow readily slides on a crust. Natural sluffing may occur on steep slopes with loose surface snow, with rider-triggered slides likely. 

    Utilize techniques to manage your sluff. Limit time spent in long-running gullies where getting caught in a sluff may make escape difficult. Choose descent routes free of terrain traps where the snow piles up deep.

    (2/3/2023)

    This image is an example of a Loose Dry slide. The top 8-10" of low-density snow slid on an underlying crust.

    Photo: Mark Dundas

Avalanche Discussion

Snowfall Thursday and overnight into Friday morning favored the Swan Range, with over 1 inch of SWE and 7+ inches at Noisy Basin. As of 0500, most other mountain locations had picked up 3-6+ inches with 0.7 inches of SWE at Stryker Ridge in the Whitefish Range. Winds shifted back to the southwest yesterday and are generally light with moderate gusts. The wind is forecast to blow from the north or northeast as a low develops east of the Divide today. Temperatures, thankfully, have fallen back to a cool, seasonable range.

The new snow and wind have bumped the avalanche danger following two days of LOW danger.  The hazard is highest in the Swan Range, where more snow accumulates, and the winds are stronger. The Flathead Range and southern Glacier Park have also done well, with the Whitefish Range lagging. Snowfall should taper off through the day, but fresh slabs will continue forming in wind-affected terrain at upper elevations.

The storm was accompanied by intense periods of precipitation. The Noisy Basin SNOTEL recorded 0.5 inches of SWE (4+ inches) in a two-hour period overnight. Snowfall rates greater than 1 inch per hour generally create instability and possible natural avalanche activity. We have rolled a storm and wind slab problem together to mitigate uncertainty. Storm slabs are problem #1 in the Swan and Flathead zones, while loose dry is the #1 problem in the Whitefish Range.

Yesterday (Thursday), Rob, Cam, and Guy explored the terrain around the Anna Creek cabin on the east side of the Swan. They reported having to manage their sluff on steep, northerly aspects where 6-8 inches of faceted, loose surface snow moved downhill easily. Blase and Jeff encountered similar conditions on their tour east of the WMR ski area. 

Upcoming event: Flathead Avalanche Friends Fest, February 21-24. Beacons & Brews, Name That Tune/Name That Avalanche, Workshop Night, Hot Dog Days, and Ultimate Après.  Check out 4 days of events: flatheadavalanche.org/event/friendsfest

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