Bollettino valanghe

Seeley Lake

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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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It’s really warm, and temperatures will rise today. All elevations will be affected. Below 6500’ the snowpack is saturated and lacks cohesion. Wet loose avalanches up to D2 in size are likely, and larger avalanches are possible. Wet slab avalanches are possible in isolated areas. Avoid crossing or passing below avalanche terrain where wet snow exists. 

Problemi valanghivi

  • Loose Wet

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

    Elevated temperatures have created an isothermal snowpack lacking cohesion at elevations below 6500 feet. Nonfreezing temperatures last night compounded the problem. Rising temperatures, rising freezing levels, and solar warming will create wet snow problems at higher elevations today. 

    As warming continues, so does the likelihood of larger loose wet avalanches. Multiple D2 wet loose slides were spotted yesterday. Avalanches could grow in size today. In some areas, wet slab avalanches are possible, such as on smooth rock slabs or the buried surface hoar in the Lolo pass area. 

    Conditions similar to the current weather resulted in a very large D3 avalanche last year in the Bitterroot, and it is within the realm of possibility today. In addition, cornices are big and will be destabilized by warming temperatures, increasing the likelihood of cornice fall.

    If you recreate in the mountains today, plan a safe entry and exit from the mountains that does not cross or pass below steep slopes with wet snow. Wet snow problems are less predictable, and standard stability tests are not applicable. As snow surfaces warm-up, and roller balls start, move to shadier aspects or higher elevations. If you are punching deep into saturated snow, you are in the wrong place.

  • Wind Slabs

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

    Strong sustained winds were transporting snow for the past three days. While transport was limited in many places due to the presence of a crust and moist snow surfaces, the possibility exists to find pockets of reactive windslab. Upper elevations below ridgelines are the most likely places to trigger windslab, but cross-loaded gullies may also hold pockets. Look for wind lips and smooth pillows to indicate wind transport. Shooting cracks indicate instability. Avoid wind loaded start zones over 35º. 

  • Persistent Slabs

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

    Primarily in the Lolo Pass area, buried surface hoar became more reactive over the weekend as new snow consolidated. The surface hoar was failing and propagating in tests, whumpfing was experienced. This layer was somewhat stubborn to human triggering. However, given the extent of the surface hoar, large avalanches are possible if you find the trigger spot. Slides could take on characteristics of wet slab avalanches as the warming continues.

Avalanche Discussion

Despite the groundhog seeing it’s shadow and being scared back down it’s hole, we currently have very spring-like conditions. Low elevation snow is rapidly disappearing, making approaches and exits more difficult. Mid elevations are saturated and losing cohesion, increasing the likelihood of wet loose and wet slab avalanches. Upper elevations were buffeted by wind, have various crusts, and windslab can be found. 

Temperatures yesterday peaked at 35º at Saddle Mountain at 7940 feet in the southern Bitterroot and 38º at the North fork of the Jocko at 6330 feet in the Southern Missions. Winds were moderate out of the west, with strong gusts.  Rain fell at lower elevations in the southern Bitterroot, and up to an inch of wet snow fell in the central Bitterroot. Luckily overcast skies limited solar warming. 

Temperatures will be warmer today, with the freezing level reaching 9000 feet. Cloud cover is forecast to be 35-40% which may or may not limit solar warming.

Below about 6500’, the snowpack did not refreeze last night. The already saturated snow will continue to lose cohesion today as temperatures rise. Yesterday wet loose avalanches were abundant. Many were reported throughout the forecast area, reaching D2 in size. Large enough to bury, injure, or kill a person. In Fred Burr canyon, wet slab avalanches had run to the ground on rock slabs. There were abundant signs of destabilizing conditions that caused some observers to choose conservative, unexposed terrain.

As temperatures rise today, stability will decrease with warming. With any luck, clouds will limit the sun; however, any clear skies and solar warming will accelerate destabilization. 

Upper elevations that stayed below freezing have crusts and windboard limiting snow transport despite strong winds. Stability was good in the central Bitterroot above 7000’. Slopes at upper elevations on shaded aspects may still hold soft dry snow but, that could change as freezing levels rise today. 

Timing and terrain use is a big part of recreating in the mountains today. Avoid areas that did not freeze overnight, move off slopes over 35º and out from under steep slopes as temperature rises, and roller balls are starting. Plan your exit from the mountains, so you have a low-angle route that does not cross over or under slide paths late in the day. 

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

Ski and ride safe

Regioni coperte