Bollettino valanghe

Rattlesnake

West Central Montana Avalanche Center
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Pericolo valanghe

Sun
Alta quota
1 · Debole
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The hazard is low throughout the Rattlesnake and Seeley Lake zones, but there is a possibility of loose wet avalanches on south and west aspects in the afternoon. Refrozen snow surfaces on south aspects could result in uncontrollable slides. Plan descents to coincide with sun softening of the snow surface before wet loose activity begins. Alternatively, look for softer snow on north aspects above 6000’. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    There is a chance of loose wet slides on solar aspects with rising temperatures today. 

    These will most likely be small and happen late in the day. They pose minimal hazard on their own, but terrain traps will increase the consequences of a slide and the likelihood of trauma.

    As temperatures rise later in the day, watch for roller balls to indicate that loose wet avalanches are more likely. If you are sinking into wet snow past mid boot, it’s time to move to shadier aspects. 

Avalanche Discussion

Today’s forecast is the first with the forecast area broken into three zones. They are the Seeley lake zone, the Rattlesnake zone, and the Bitterroot zone. When applicable, each will contain information specific to the zone and different hazard ratings when warranted. We are excited about this update as it allows us to present information on avalanche conditions more precisely. 

The past 48 hours have seen quite a swing in temperatures. Thursday saw highs of 40º at 8000’ in the Southern Bitterroot and 37º at 7400’ in the Rattlesnake. Low elevations had significant warming, with temperatures reaching 54º in the valley. 

Evidence of the warming is present at all elevations. An icy sun crust is present in the Rattlesnake and southern Missions. Cornice fall in the southern Missions triggered loose wet slides that entrained snow. Lolo Pass has a supportable crust, even on north aspects. The central Bitterroot has various crusts, windboard, and slide for life conditions in the alpine. Loose wet avalanches closed Hwy 93 south of Lost Trail Thursday. 

Despite the warming, some north aspects above 7000’ have crust-free dry snow, and south aspects in the Rattlesnake have carvable snow below the zipper crust. Wet slides were limited in upper elevation terrain throughout the forecast area. 

Yesterday, wind slab was mostly nonreactive except for stubborn pockets in very steep and unsupported terrain. Due to widespread crusts and windboard, no snow is available for further wind slab development. These same crusts, most prominent in the Bitterroot, pose the hazard of uncontrollable slides if you lose an edge. Plan for exposed terrain, crampons and ice axes are a good idea.

Today temps will reach up to 43º above 6000’, and winds will stay light with the occasional strong gusts. The skies will be clear. 

We are in a spring-like pattern of cold nights and warm days. Solar warming won’t be as strong as later in the spring but will affect southerly aspects. Time your travel to climb on frozen snow and descend on sun softened snow. Leave the decent too late, and you could be dealing with loose wet avalanches. Too early, and you could be dealing with dangerously icy conditions.

As always, we’d love your observations. If you get out in the mountains today, please submit them here.

Ski and ride safe

 

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