Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
Open full map
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The wind is drifting snow into fresh slabs along ridges, saddles, and other prominent terrain features. Wind-sheltered terrain may hold isolated small slabs. You could trigger slides from gentler terrain below, above, and to the sides of steep slopes. Pull back from steep slopes if the snow surface cracks around your feet or machine. 

 

Problemi valanghivi

  • Wind Slabs

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

    The winds have been strong enough to transport new snow at upper elevations. Look for fresh slabs forming below ridgelines and saddles or in cross-loaded gullies. You may find small isolated slabs at middle elevations in areas favored by wind. 

    Fresh snow has fallen or drifted onto weak layers like facets or surface hoar in many locations, adding to its instability. Due to the underlying weak layer, slabs may be triggered remotely or from a distance.

    If you suddenly notice your boards or machine not sinking as deeply into the new snow, you have stumbled onto a slab. Use hand pits or small inconsequential slopes to test how well the fresh snow bonds to the old surface. Cracking in the snow surface indicates an unstable slab and is a clear signal to seek out lower-angle or sheltered terrain.

    (12/3/2023)

    We found thick, fresh slabs on leeward terrain features. Due to the wind speed and duration these slabs are dense (1Finger hard).

    Photo: Sarah Williams

Avalanche Discussion

Put your hands at 10 and 2. We’ve been hot-rodding around for several weeks now, but as new snow starts to stack up on weak surfaces, it’s time to consider increasing your margin for safety. Snowfall totals in the last 24 hours were once again modest. Tunnel Ridge, in the northern Flathead Range, and Flattop, in Glacier National Park, picked up 2 inches of new snow. Other sites across the advisory area are reporting an inch or less. Upper-elevation winds have been sufficient to drift the fresh snow: Aeneas Ridge, in the Swan Range, has averaged over 30 mph with gusts exceeding 60 mph during the last 8 hours. 

A pair of observations from yesterday (Friday) found the new snow riding nicely on top of a supportable crust. Sarah and I were in the Swan Lake area. There, we found up to 6 inches of recent snow consisting of heavily rimed particles and graupel. Still, moderate gusts were drifting new snow into thin, stubborn wind slabs in favored locations along upper elevations ridgelines. Our most significant hazard, however, was still from thin coverage on our descent through middle elevations.

In locations favored by recent snowfall, you might find isolated slabs in wind-sheltered terrain. Incoming snowfall tonight will continue to build thicker slabs on top of weak layers and may increase avalanche danger into next week.

Regioni coperte