Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The snowpack continues to adjust to the heavy load from the recent warm, wet storm. Dangerous avalanche conditions remain in areas of wind drifted snow at mid and upper elevations. You can trigger a slide large enough to bury or injure you in stiff, dense snow. Continue to give the snowpack time to strengthen while enjoying the bountiful powder in sheltered locations.

Problemi valanghivi

  • Wind Slabs

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

    The recent storm left us with plenty of snow available for transport at mid and upper elevations. Southerly and westerly winds during and following the storm have been plenty strong enough to transport this snow onto leeward aspects. Riders and avalanche class students noted wind transport on Saturday in the Whitefish Range and the Flathead Range. Expect to find evidence of fresh slabs increasing as you gain elevation, such as textured, dense snow that your machine or skis barely penetrate. Utilize hand pits to determine how well the surface snow bonds to the underlying layers. Riders reported excellent soft conditions in sheltered terrain Saturday, and you would be foolish not to follow their lead.

    (1/8/2022)

    The FOFAC motorized Level 1 avalanche class found a shear plane on a wind-loaded slope at the new snow/old snow interface.

    Photo: Mark Dundas

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–3

    We have generally enjoyed a strong right-side-up snowpack this season. However, layers of weak snow and crusts in the snowpack may present themselves following the recent loading event. This combination can be found 2-4 feet below the surface while deeper in the pack depth hoar, and another facet/ crust from early December lurks. Cam reported loud collapses Friday, which may result from failure in one of these layers. The recent loading event stressed these weak layers, and your or your machine's weight may tip the balance today. Triggering a slide on one of these layers or a surface slide that steps down will be large and destructive.

    (1/5/2022)

    Layers of small facets did not propagate in large column tests, but may be more reactive with heavy new loading.

    Photo: Nelson

Avalanche Discussion

An impressive storm exited our region early Saturday morning after depositing around 3 inches of water at low and mid-elevations in the northern Whitefish Range, over 3 inches in central Glacier Park, and about 2 inches in the northern Swan. On Thursday, we increased the avalanche danger to HIGH in all ranges due to the warm pacific storm, which followed prolonged cold weather and low-density snow. The snowpack underwent rapid change twofold - warming temperatures and copious moisture.

The moisture shut off partway during the storm in the Swan Range, which allowed us to drop the danger to CONSIDERABLE on Friday. The remaining moisture exited our region early Saturday morning, resulting in a CONSIDERABLE danger across the forecast area Sunday. The storm snow has had some time to strengthen, and we have dropped the storm slab from today's problem list. We have added a wind slab as today's number one avalanche problem with plenty of snow to transport and no shortage of recent windy conditions. 

Observations Saturday were generally from mid-elevation sheltered locations. Outside of WMR, The Patrol Fund Level 1 avalanche class found consistent non-propagating results with moderate force in ECTs and CTs on all aspects, with failure occurring ~45cm from the surface at the storm snow/old snow interface. The layer of concern appeared to be a thin layer of preserved stellars and hexagonal plates resting atop the old snow interface. The FOFAC motorized Level 1 class found at the Olney trailhead it had snowed throughout the storm and not turned to rain as many low-elevations had. We found similar results to the Patrol Fund class with non-propagating failure occurring at the old snow/new snow interface. Riders in the Flathead Range reported a rain crust as high as 4800 feet but sweet riding conditions above that in sheltered mid-elevation terrain (Example 1, Example 2).

Regioni coperte