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
2 · Moderato
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Today will be an overlapping mix of avalanche problems  as temperatures warm and another round of snow or rain arrives this afternoon. Expect sensitive wind slabs in wind affected terrain, storm slabs in sheltered terrain and wet snow avalanches if the snow turns to rain. 

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

If you see avalanches, shooting cracks, or rain on snow  avoid avalanches by sticking to slopes less than 30 degrees in slope angle.

Problemi valanghivi

  • Wind Slabs

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

    Another round of new snow will arrive this afternoon with moderate to strong west winds. This will continue to build wind slabs on top of the wind slabs that formed in the past 48 hours. Wind slabs are very likely on east aspects at both mid and upper elevations. Expect these slabs to be reactive again today. 

    Observations yesterday showed significant snow transport and slab formation in east facing terrain. Wind speeds were high enough at times to reach down into mid elevations and transport snow low on slopes or in areas not usually associated with wind slabs. 

    Identify wind slabs by looking 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. 

    Avoid wind slab avalanches by sticking to slopes under 30 degrees in slope angle or terrain unaffected by blowing snow and wind.

    (3/22/2025) Small wind slab triggered remotely at Lolo Pass. Public Observation. 

  • Storm Slabs

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

    Storm slab avalanches will be possible in areas unaffected by wind. As temperatures rise this afternoon into evening, snow densities will become inverted with higher density snow falling on top of lower density snow. Inverted or “upside down” snow densities can lead to sensitive conditions and widespread storm slabs within the new snow. Warmer temperatures or short periods of sun also have the potential to help new snow consolidate into a storm slab.

    Yesterday, new snow totals varied, even within the same zone as much of the storm came through as bands of precipitation rather than one large storm front. If you find 6 inches or more of new snow, expect the possibility of storm slabs. 

    Storm slab problems are short lived with peak sensitivity lasting hours but it can still be possible to trigger stubborn storm slabs for a day or two after peak sensitivity has passed. 

    Even small storm slabs can be dangerous if they push you into terrain traps like streambeds and gullies or carry you through trees and rocks. 

    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.

  • Loose Wet

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

    There is a possibility of the snow turning to rain by late afternoon as the snow line climbs to 6000'.  If rain falls onto fresh snow, natural wet snow avalanches are likely. The uncertainty with this problem revolves around whether or not the snow line will climb today, and if a rain on snow event will happen. 

    If you are out in the mountains and feel the snow transition to rain, stay off steep slopes and out from underneath avalanche terrain as wet snow avalanches are possible.

Avalanche Discussion

Another day, another round of snow. The difference today will be warming temperatures and higher snow densities. Spring storms can have more uncertainty than winter storms and there is a possibility of rain at mid elevation today. 

The northern Bitterroot, Rattlesnake, and Seeley look like they will get the most snow today, with .5 to 1.5 inches of SWE (snow water equivalent) by Monday. How much snow this will translate to will be highly temperature dependent. Colder atmospheric temperatures will make low density snow while warmer temperatures will make less snow but at a higher density. 

Expect a high degree of spatial variability today. The most important thing will be to pay attention to your surroundings. If you see red flags like shooting cracks or fresh avalanches, stick to slopes less than 30 degrees in slope angle. Additionally if you find yourself getting rained on, get out of avalanche terrain. 

Look for growing cornices today along ridgelines, and do not travel below them. Dense spring snow with wind can build large overhanging cornices rapidly. If one of these cornices failed, it would also likely trigger an avalanche. 

We have dropped the persistent slab problem from the forecast. Pockets of rounding January facets might remain in very specific terrain,  however, no avalanches have been reported in a month and the problem has become unreactive. Recognize that where you are traveling may be an outlier with a more complex snowpack than the rest of the zone. It is always worth digging in the snow, even if you don’t suspect anything. If you encounter weak or sugary snow with a slab above, the best advice is to avoid avalanche terrain. 

Our last scheduled product for 2024/2025 will be Monday March 31st. We will update the avalanche product through April whenever conditions warrant. 

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.

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