Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Wed
Alta quota
1 · Debole
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

The few inches of new snow that fell overnight is not enough to increase the avalanche danger. The main avalanche concern remains triggering a slab avalanche on weak layers buried 6 to 18 inches below the surface on shaded aspects that don’t hold a surface crust. If the precipitation forecast verifies tonight, expect the avalanche danger to increase to Moderate.

Problemi valanghivi

  • Persistent Slabs

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

    The most recently reported avalanche failing on buried weak layers was between February 7th-9th during periods of heavy wind loading. Snowpit tests from north-facing aspects this weekend show this layer can still propagate when collapsed. If you head out today searching for colder snow on northerly aspects, choose slopes that are concave or planar in shape. Choose terrain with clean runouts to reduce the likelihood of a triggered avalanche having large consequences. When in doubt, choose slopes with angles less than 35 degrees or change to solar aspects and ride where a surface crust has the snowpack locked in place.

    (2/12/2022)

    Riders opted out of skiing a steep northeast slope after noting propagation in their snowpit tests. ECTP18@25cm below the surface (x2) on a thin well-preserved graupel and facet layer at the interface between a 1F wind slab (above) with 4F rounding facets layer (below).

    Photo: Zach Miller

Avalanche Discussion

A fresh coating of snow fell throughout the forecast area overnight. Whitefish Mountain Resort took the lead with roughly 3 inches of new snow. Tunnel Ridge in the Flathead Range and Noisy Basin in the Swan Range both picked up an inch of new snow. Wind speeds were generally light in the Flathead Range and Glacier National Park. Remote weather stations in the Whitefish Range and in the Swan Range recorded average wind speeds around 12 to 20 mph with gusts as high as 50 mph on Mt. Aeneas.

Today, we will likely see an additional inch of new snow with light wind speeds. New snow will sluff easily on recently-formed melt freeze and rain crusts. I wouldn’t be surprised to find small pockets of wind drifted snow on the leeward side of exposed ridgelines. Both of these hazards will be easy to manage and should be harmless in size. However, they won’t be harmless if you get pushed around by debris above consequential terrain features. On Sunday, a skier was caught, carried over a cliff band, and partially buried in Colorado (report). This is a reminder to us how small avalanches can have large consequences in the wrong kind of terrain. Luckily, this rider was uninjured and able to walk away.

Persistent weak layers buried 6 to 18 inches lurk below the surface. I am still hesitant to jump onto steep, consequential slopes that harbor these weak layers. That's slopes that face north where a surface crust does not exist. Safer options are slopes that have a strong melt-freeze crust.

Another shot of snow is expected tonight. Snow accumulations may reach 6 to 9 inches in the Swan Range, with less expected in the Flathead and Whitefish Range. The avalanche danger will rise to Moderate overnight if the weather forecast verifies. 

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