Bollettino valanghe

Bitterroot

West Central Montana Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

The temperature remains elevated, especially for the southern reaches of the forecast area, and water continues to saturate, trickle and pool in the mid and lower elevation snowpack. The worst of the natural avalanche cycle has likely passed. However, the weight of you or your machine could still trigger a large lingering wet avalanche today. You may encounter dry avalanche problems like lingering storm slabs if you travel to high elevations.  

Problemi valanghivi

  • Wet Slabs

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

    Temperatures remain elevated, and the snowpack is predominantly saturated below approximately 7,000 feet and 8,000 feet in the Bitterroot. Water is likely pooling and lubricating buried melt-freeze crusts and triggering large wet slabs are still possible. Uncertainty is high for how many wet avalanches have already run and what it will take for more of them to release.   Avoidance is our best option. Stay off slopes that you are sinking past your boot in wet sloppy snow and minimize travel under the base of slopes capable of sliding until the temperatures cool back down. Steep road cuts that haven't already released come to mind as a potentially dangerous spot. 

    (3/2/2022) Example of a wet slab and storm slab in the Lost Horse drainage. Photo: David Fox

  • Storm Slabs

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

    Higher elevations may harbor lingering slabs of storm snow capable of producing avalanches deep enough to bury you. The snow fell over various surfaces, including dry faceted snow and melt-freeze crusts that could act as a smooth sliding surface for avalanches to run on. The higher temperatures are likely keeping them stubborn to trigger, but it’s still possible on slopes steeper than 35 degrees. Use small safe, representative slopes for tests and avoid avalanche terrain if you see shooting cracks.

    (3/2/2022) Example of a storm slab near Wahoo Pass. Photo: David Fox

Avalanche Discussion

We've had heavy wet snow, rain, and elevated temperatures for the past four days. Snow levels have hovered around 6,500 to 8,000 feet, with the southern Bitterroot seeing the warmest temperature and highest snow lines. Since Sunday (02/27), a whopping 2 to 3.8 inches of water fell throughout the forecast area. Temperatures stayed elevated in the mid 30ºF throughout the area last night. The Rattlesnake overnight average was 36ºF. Winds have stayed light out of the southwest and switched to southeast early this morning. 

It's not cooling off much yet, but the weather models show slightly cooler temperatures and snow levels dropping to 6,500 feet for Seeley Lake, Rattlesnake, and Central Bitterroot zones today. Snow levels in southern Bitterroot will stay near 7,000 feet. 

In general, the natural avalanche cycle has already peaked, leaving an impressive amount of debris strewn about. We found debris from a wet loose avalanche at 5,000 feet in Bass Creek, wet saturated snow, and widespread running water under the snowpack at lower elevations. Jeff found class 3 wet slabs had occurred in all of the big avalanche paths in Lost Horse drainage. These ran nearly full path. Natural storm slabs ran sometime during the storm's peak, likely Monday (02/28), failing above a sun crust formed a little over a week ago (02/22). Trask mentioned that he could easily start wet loose avalanches with a single toss of a snowball, and widespread rollerballs and debris from wet avalanches were in the Rattlesnake. 

We were finding reactivity on persistent grains in drainages in the vicinity of Gash (Central Bitterroot) before the storm. Likely, everything that could have gone on this layer has already been released, and your weight is unlikely to test this layer further than it has recently been tested. The forecasted cooler temperatures in the coming days will lock it in place. 

Ski and ride safe

Regioni coperte