Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

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Sotto il limite
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In sintesi

Winds continue to drift snow into thin slabs. Yesterday (Tuesday), a rider in the northern Whitefish Range triggered small avalanches in wind drifted snow. Riders in the Flathead Range found unreactive fresh slabs of drifted snow. Those observations are key information for us to utilize today. Slopes sheltered from the wind will provide a safer and more quality experience.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–1.5

    Wind speeds increased yesterday (Tuesday) and blew what little snow there was to transport into thin slabs.  Observers noted drifting above 6000 feet in the Flathead Range, with no signs of instability with stomping on small test slopes. An observation from the northern Whitefish Range showed reactive slabs in wind-drifted snow that failed on buried facets. Today, Steer around small pockets of wind drifted snow. If in doubt, hedge your bets on slopes sheltered from the wind. You can also choose windward aspects for a safer option.

    (1/15/2023)

    Cracking in freshly wind-drifted snow

    Photo: Kevin Oberholser

Avalanche Discussion

Dribs and drabs of snow are piling up above 6000 feet. Since January 9th, Noisy Basin in the Swan Range has picked up 3.1 inches of snow water equivalent (SWE). Stahl in the northern Whitefish Range was not reporting for a couple of days, but is still showing 1 inch of SWE. Flattop in Glacier National Park is showing 1.5 inches of SWE. This snow came after an extended dry spell at the beginning of January. Remember that distant memory of low danger and sunshine with 8 to 20 inches of powdery snow?

This brief overview of the last two weeks paints a picture of our upper snowpack today. The 4 to 20 inches of snow faceted on many shaded aspects at the beginning of January. During that time, photos of feathery surface hoar trickled in. The sun shined and warmed solar aspects, cooking the snow surface and forming a thin sun crust. This is what all the recent snow is resting on.

Observations from all three regions show a developing Persistent Slab avalanche problem. We made the transition to calling it that in the Swan Range, where enough snow piled up above these weak layers for it to be problematic. The BNSF Avalanche Safety Program found propagating pit results on faceted snow above the Christmas Crust, which is now buried roughly 22 inches below the surface. I observed a crown near Essex that I suspect failed on this layer during the recent rain event. A rider in the northern Whitefish Range triggered three small slabs in wind-drifted snow. These all failed on layers of faceted snow 5 to 10 inches below the surface.

Our primary concern right now for Persistent Slabs is in the Swan Range. With that said, persistent weak layers buried below the surface do exist in the Whitefish Range, Flathead Range, and Glacier National Park. If more snow piles up, or we continue to see signs of instability, this may become a problem in those ranges shortly.

Regioni coperte