Bollettino valanghe

Whitefish Range

Flathead Avalanche Center
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Pericolo valanghe

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

Triggering a large avalanche on a buried weak layer is unlikely, but not impossible at upper elevations. Solar radiation and increasing temperatures will warm the surface snow throughout the day. Avoiding being caught on sunny afternoon slopes by planning for an early exit or moving to shady aspects when you see pinwheels or rollerballs.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2–3

    Triggering a Persistent Slab avalanche is unlikely. For most areas in our advisory, observational data supports this problem as a low-likelihood, but high-consequence avalanche. Reduce your odds of being unlucky by selecting terrain away from rocky outcroppings or areas with possible trigger points like convex rollovers or shallow patches of snow due to sun or wind scouring.

    Keep your riding partners and yourself in check by continuing to evaluate the terrain as you travel. Stick with uniformly covered slopes that hold a deeper snowpack. When you are in doubt, riding lower-angle slopes is a great way to reduce your worry and your risk.

    We’ve been tracking several buried weak layers in the snowpack that are capable of producing a destructive avalanche. See the labeled snow profile photo for reference.

    • A weak layer and crust combination from mid-January has been responsible for most of the Persistent Slab avalanches. This layer is generally found 2-4 feet below the surface. (Labeled in pink in the photo).
    • Faceted snow resting on the Christmas crust (labeled blue in the photo).
    • Faceted snow formed in November near the bottom of the pack is responsible for the recent snowmobile-triggered slide in the northern Whitefish Range and the natural slide on Elk Mountain (see brush at the bottom of photo).

    (2/28/2023)

    Wahoo drainage. Christmas crust was 100cm below the surface. Mid-January was 85cm below the surface.

    Photo: sw

Avalanche Discussion

We received one report of a failing cornice in the Flathead Range and no human-triggered avalanches on Tuesday, thanks largely to cool ambient daytime air temperatures. In addition to this sunny but cooler weather, solar aspects have been through several days of a melt-freeze cycle and thus limiting today’s wet avalanche activity. The general consensus of yesterday’s (Tuesday) observations report that overnight temperatures froze the warmed surface snow on sunny aspects into a hard crust. This supportable crust made for speedy travel conditions and likely stayed firm, except for the true south-facing slopes. Many riders reported finding unconsolidated soft snow on northerly shaded aspects, which is great news to have dry snow stashes on March 22nd.

For today, the forecast calls for another day of mostly sunny skies. Don’t forget to pack sunscreen and keep in mind that spring conditions warrant caution around three avalanche problems associated with solar radiation and increasing temperatures.

  • Wet Loose
    • Warming surface snow that becomes wet increases the instability of the snowpack. Avoiding confined terrain or gullies that could catch and carry you into places you don't want to go. Rollerballs or pinwheels are good clues that the snow is becoming more unstable.
  • Cornices
    • Large cornices hanging over ridgeline slopes tend to fail during the heat of the day and deserve a wide berth, both from below and while traveling along ridges.
  • Glide cracks
    • Glide cracks continue to be reported throughout the region and are expected to widen as the whole snowpack slides over the wet, smooth ground below. Staying away from glide cracks and out from under them is the best and only travel advice.

 

FOFAC Event: March 30th, 2023– Whether you're chasing tan lines, big lines, or both, you'll learn something valuable from FAC Lead Forecaster Mark Dundas about spring avalanche problems, how they differ from winter problems, and how to manage them. We will also discuss current conditions and concerns (or lack thereof!) with our spring snowpack. Enjoy a cold brew from Bias Brewing and a scoop from Sweet Peaks Ice Cream. The event is free and open to everyone. Begins at 6 pm.

FOFAC Recording March 15th, 2023-- Cam's State of the Snowpack link here

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