Bollettino valanghe

Bitterroot

West Central Montana Avalanche Center
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Pericolo valanghe

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

In sintesi

Large natural avalanches are possible today, and human triggered avalanches are likely. Expect to encounter  large wind slabs at upper elevation and storm slabs in non wind affected terrain.

It will be possible to trigger avalanches remotely from below or to the side. 

There will be great skiing and riding on lower angle slopes. Travel in avalanche terrain is not recommended today. 

Considerable danger is the largest spectrum within the avalanche danger chart. Lolo Pass and the Rattlesnake are on the low end of considerable danger. By this afternoon, the Bitterroot crest and southern Bitterroot could approach high danger.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    6 inches of new snow yesterday and last night built fresh wind slabs on the north and east aspects. Today, expect these slabs to increase in size and sensitivity as another foot of snow falls with increasing southwest winds. Wind slabs along the Bitterroot crest could be up to D2.5 in size, breaking 3-4 feet deep and running fast on the crust interface. 

    To identify wind slabs, look for areas of smooth or pillow-like snow. If you poke or dig into the snow and find a slab at the surface with a hollow feeling, or see cracking around your skis or sled, you've likely found a wind slab. 

    To avoid wind slab avalanches, stick to slopes under 30 degrees in slope angle, or terrain unaffected by blowing snow and wind.

    (3/15/2025) Flagging or blowing snow off of peaks is an indicator of strong winds blowing snow and building fresh wind slabs. 

  • Storm Slabs

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

    Reactive storm slabs are likely today as the new snow struggles to bond with weak snow and crusts at the interface. Yesterday, observers noted natural storm slab activity in the Rattlesnake. Today, storm slabs will be most prevalent in the central and southern Bitterroot where 10-15 inches of new snow is expected. 

    Storm slab problems are short lived, with peak sensitivity lasting hours. Even after the peak sensitivity period has, it will still be possible to trigger a stubborn storm slab for a day or two, especially if new snowfall continues. 

    Look for shooting cracks or small avalanches on test slopes. If you see these, enjoy low angle powder skiing by sticking to slopes less than 30 degrees in slope angle and be cautious of convex rollovers or terrain traps.

    (3/15/2025) Public Observation: Rattlesnake upper grant creek. Fresh storm slab failing naturally at cliff base. 

  • Persistent Slabs

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

    Triggering a larger persistent slab avalanche that fails 3-5 feet deep has become unlikely. Smaller avalanches today may step down and impact these deeper buried layers. 

    Specific pockets of poor snowpack structure remain with buried January facets, and facet crust combinations. This problem still lingers in areas with rocky convex rollovers, however, even in these areas snowpit tests have become increasingly unreactive. You are unlikely to see any red flags like shooting cracks, whumphs, or feel collapsing before an avalanche occurs. 

    If you find weak or sugary snow with a slab above, avoid the problem by skiing or riding elsewhere.  If you choose to ski or ride that area, stick to low angle slopes, avoid convexities, and avoid likely trigger areas.

Avalanche Discussion

Today is a great day to enjoy some low angle skiing and riding! The storm will park itself over West Central Montana, especially from Lost Trail pass to the central Bitterroot where 10-15 inches of snow could fall today. Further north, snow totals taper off with 5-6 inches expected in the Rattlesnake and Seeley zones. Though totals are uncertain, more snow is expected tonight as the cold front arrives. 

Seek out terrain sheltered from the wind as ridgetop gusts in the 30s or even 50s around Lost Trail are possible today ahead of the cold front. 

The good news about most of the avalanche problems today is that they are short lived, with peak sensitivity measured in hours or days, not in weeks. With that, patience will be the best tool you have. Red flags like fresh avalanches, shooting cracks, or collapsing will be obvious. Use terrain to your advantage and avoid avalanches by sticking to slopes less than 30 degrees in slope angle. 

We are not anticipating a valley rain event today, but spring weather can be unpredictable. If you find yourself sinking into wet unsupportable snow, or  in a rain on snow situation, you should get out of avalanche terrain.

Win a Garmin inReach Mini 2 – Support Your Avalanche Center with Every Observation!

We’re excited to offer a fantastic opportunity to win a Garmin inReach Mini 2 simply by sharing your field observations with us!

Starting today, Saturday, March 8th, 2025, every Public Observation you submit through Missoulaavalanche.org automatically enters you for a chance to win this excellent, compact satellite communicator.

The winner will be drawn on May 2nd, 2025, during Missoula Gives!

Each Public Observation counts as an entry, so the more you submit, the better your chances of winning! Your valuable observations are crucial in helping us provide accurate avalanche forecasts, ensuring everyone stays informed and prepared for safe, enjoyable backcountry adventures.

Thank you for your continued support of the West Central Montana Avalanche Center. Submit your observations for your chance to win and positively impact your forecast!

Ski and ride safe.

Regioni coperte