Bollettino valanghe

Bitterroot

West Central Montana Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

This forecast is issued on a non-standard day due to elevated avalanche hazards and uncertainty with wet snow problems.  Wet snow, rain, and warm temperatures continue to saturate the snowpack and elevate avalanche hazards. Large wet avalanches and storm slabs remain likely. Persistent slab avalanches are possible. Travel in avalanche terrain is not recommended. Avoid being on or under all terrain greater than 30 degrees.

Problemi valanghivi

  • Wet Slabs

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

    Rain, high temperatures, and elevated freezing levels continue to saturate the snowpack. As the snowpack loses cohesion and water pools on buried melt-freeze crusts, wet loose and wet slab avalanches are likely. Just how much wet and warm it will take for them to release is unknown. Wet problems are hard to predict and can't be assessed with standard snowpack tests. Avoidance is the best option. Avalanches could run into mature forests, valley bottoms, and other areas not easily identified as avalanche terrain. Travel in avalanche terrain is not recommended. Stay well away from the base of slopes capable of sliding until it stops raining and temperatures cool back down.

  • Storm Slabs

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

    Snowfall and southwest winds are loading slopes above approximately 7,000 feet. The snow is falling over various surfaces, including dry faceted snow and melt-freeze crusts. Storm slab avalanches remain likely and continue to grow in size. Travel in avalanche terrain is not recommended. Avoid slopes over 30º and stay well away from the base of avalanche slopes.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3.5

    The added weight from heavy wet snow and rain may reawaken buried persistent layers and cause very large avalanches in the central Bitterroot. Drainages in the vicinity of Gash are most suspect, but warmth and loading may weaken layers outside of this, such as the deeply buried facets in the southern Bitterroot. Slides on these layers would be unsurvivable and could run very long distances. Travel in avalanche terrain is not recommended, persistent slides may be triggered from below and the sides, stay well away from the overhead hazards.

Avalanche Discussion

We are entering our third day of elevated temperatures, rain, and snow. Elevations below approximately 7,000 feet and 8,000 feet for the southern Bitterroot have not received freezing temperatures since Monday (2/28). The snowpack has been seriously stressed, and we don't yet know the extent of the impact. Loading will continue today in the form of rain and snow. Many avalanches have likely released, and many more are likely waiting to release. Continued snowpack saturation increases the potential for very large wet slides. Wet snow problems add to the complexity and uncertainty of avalanche assessment, and travel in avalanche terrain is not recommended. Besides, it's sopping wet out there, and skiing and riding conditions are deplorable. Now is a great time to give the legs a break. Once we get a solid refreeze, the snowpack will lock up, and the hazard will drop to a predictable and manageable level.

  Weather stations show continued rain and elevated temperatures. Continued deterioration of our snowpack is occurring. Temperatures have remained in the mid to upper 30s°F since Monday (2/28). In the past 24 hours, 34°F is the lowest temperature recorded by Snowtel throughout the forecast area. Winds have stayed light with moderate gusts out of the south and west. 

In the past 24 hours, remote weather stations show 1.6 inches SWE and a loss of 3 inches in snow depth for the North Fork of the Jocko (Seeley Zone). The Rattlesnake received 0.5 inches SWE and no snow at Stewart Mountain. Lolo received 0.4 inches SWE and a loss of 3 inches in snow depth. Twin Lakes (Central Bitterroot) received 1.4 inches SWE and a loss of 4 inches in snow depth. Saddle Mountain (Southern Bitterroot) received 0.8 inches SWE and no snow at 7,940 feet. Precipitation with a loss of snow depth indicates rain.

 Weather models show temperature beginning to cool off sometime late this evening. The transition will be slow as colder air moves with a north-to-south progression. We'll have a more detailed forecast for you tomorrow with observations from our field day today. 

Ski and ride safe.

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