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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In sintesi

It is possible to trigger a large avalanche breaking 1 to 3 feet deep. Slides are most likely - and will be larger - on steep slopes exposed to this week's winds. Recent avalanches, cracking, and collapsing are signs of instability that should steer you to low-angle terrain. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2.5

    Yesterday (Thursday), observers noted calm winds and a lack of blowing snow. Small (D1) natural and human-triggered soft slab avalanches occurred on steep slopes where the recent low-density snow was stiffened by wind. Winds will shift to northeasterly today and could cause similar conditions on slopes typically sheltered from the wind. You could find larger slabs as you climb higher. Recent avalanches, cracking, or collapsing are clear signs of unstable snow and should steer you toward lower-angle slopes.

    Several parties also found stubborn hard slabs hidden beneath the recent snow. These slabs have been slow to heal due to cold temperatures and because they are resting on a weak layer of snow formed in January. These slabs could break 1 to 3 feet deep, propagate further across the slope than expected, or fracture well above you. Probe around with a ski pole, hand, or shovel to verify where these slabs exist. 

    A large (D2) natural avalanche in John F Steven Canyon likely failed on Tuesday night or Wednesday morning on the January facet layer. 

     

    (2/6/2025)

    Skier triggered small (D1) soft slab on a steep slope exposed to recent wind.

    Photo: Flathead Avalanche Center

Avalanche Discussion

A dry January followed by a snowy start to February has caused a pair of developing hazards:

  1. Shallow instabilities within the recent storm snow.
  2. Potential for large avalanches on weak snow formed in January.

During the last week, we've used the Wind Slab problem to capture both these hazards since wind-affected slopes have been the only locations where recent low-density snow is stiff enough to produce a slab.  Light to moderate winds will continue to stiffen and thicken slabs throughout the day. As recent snow continues to settle, triggering slabs that fail on January's weak layers may become more possible. However, this process will be slowed by current and forecasted cold temperatures.

In the Whitefish Range, we've reached a fork in the road. Recent observations have found buried surface hoar roughly 1.5 feet deep, and pit tests have begun to show some unstable results. It might be early, but we've elected to list Persistent Slab.  Nearby zones in the Idaho Panhandle and Canada have seen natural and triggered avalanches on buried surface hoar.  

You can expect some sluffing in the new snow on very steep slopes.  These will only be hazardous if you are knocked off your line and swept into trees, over a cliff, or deposited in a gully.

 

Regioni coperte