Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

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

In sintesi

New snow and wind have formed slabs below ridgelines. Places with more than 8 inches of new snow will produce the thickest and most dangerous slabs. It is still possible to impact buried weak layers on shaded slopes above 5000 feet. Travel in areas sheltered from the wind will harbor the safest snow.

Problemi valanghivi

  • Wind Slabs

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

    Recent wind and new snow have formed fresh slabs on both typical and atypical sides of ridges. Yesterday(Thursday) winds from the southwest loaded N/NE slopes. Overnight winds shifted and are currently loading S/SW slopes. Exposed ridgelines, sidewalls of gullies, and mountaintops are places to find freshly drifted snow. Skirt around areas where you observe dunes or start seeing shooting cracks.

    Areas where 8 inches or more of recent snow has fallen will increase the hazard. The Whitefish Range and areas near the Continental Divide are near or above this threshold.

    Sneaking in below areas of wind drifted snow will be the best bet for avoiding triggering wind slabs like this.

    (2/28/2024)

    Photo: Rob Millspaugh

  • Persistent Slabs

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

    In areas without a supportable surface crust, it remains possible to impact a weak layer buried 2 to 4 feet. In general, these slopes will be at an upper elevation and face north. Places with complex, rocky terrain and unknowing shallow spots are slopes where you are more likely to trigger a buried weak layer. Seeing recent tracks does not necessarily equate to safety, as avalanches involving the buried weak layers have often been skied and ridden on by several people. 

    (3/15/2024)

    Areas with vaired snowpack depth, rocky and complex-terrain are the most vulnerable to failing on a buried weak.

    This is the crown of a very large (size 3 of 5) Hard Slab that failed on a steep, unsupported southeast slope on March 15th. 

    Photo: BNSF Avalanche Safety

  • Loose Dry

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

    Recent snow will run fast and be easy to trigger on the buried crust from last week's warm weather. Sloughing is easy to manage if your plan is to let snow run beside you rather than over you. Places where you feel the crust supporting you or your machine are slopes most likely to be an issue. 

    (2/10/2024)

    In the 8" of recent dry snow resting on a stout crust, loose dry slides were easy to trigger intentionally. 

    Photo: Mark Dundas

Avalanche Discussion

Springtime storm skiing is upon us. Yesterday(Thursday) snow fell throughout the day and into the night with the northern Whitefish Range receiving the gold medal and 7-9 inches. Silver was handed out to central Glacier Park and the Flathead Range with 6-8 inches and the Swan Range bringing home bronze with 2-3 inches. 

Harken back to balmy times just a few days ago and envision the crust that formed on W-S-SE slopes after temperatures dropped below freezing. The new snow that has fallen on a slick bed surface will likely sluff, given a trigger. 

Uncertainty remains constant in regards to the buried weak layers. Reports of dry snow only a few inches below the surface on shaded aspects during the heatwave means moisture didn’t make its way through the snowpack. The resulting “crust” that formed on these shaded slopes is likely not supportable which means the weight of a person or machine could still impact the weak layers buried 2 to 4 feet below the surface. Spatially speaking it is like stumbling across a needle in a haystack. The only way not to prick your finger is to remain patient and give these specific slopes more time to stabilize.

Help avalanche researchers! The Colorado Avalanche Information Center, the Avalanche Research Program at Simon Fraser University, and the U.S. National Science Foundation National Center for Atmospheric Research are researching how skiers, snowmobilers, snowshoers, ice climbers, and anyone else who travels in the backcountry interpret avalanche forecast information. Part of this research includes a specific survey to better understand how useful avalanche forecast information is for trip planning. 

Completing this survey will take approximately 20 minutes. Thank you for sharing your feedback to help us improve avalanche risk communication. 

 

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