Bollettino valanghe

Seeley Lake

West Central Montana Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

On steep slopes, it's possible to trigger avalanches of wind drifted or unconsolidated loose dry snow. Carefully assess stability before committing to steep terrain. Steer around areas steeper than 35 degrees that harbor snow that doesn't bond well to underlying crusts to avoid today's avalanche problems. 

Problemi valanghivi

  • Wind Slabs

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

    In recent days, variable winds formed thin to medium thick drifts in exposed middle and upper elevation terrain. A small storm will bring more productive easterly winds and light snowfall. It will be possible to find wind slabs that are sensitive to the weight of you or your machine on slopes steeper than 35 degrees today. 

    Watch for wind lips and pillows around gullies that indicate wind transport and loading. Feel for dense or hollow-sounding snow at the surface while you travel. Approach wind-loaded slopes with a high degree of suspicion. Test small, safe, representative slopes for reactivity before stepping into bigger or more open terrain. Shooting cracks and collapsing indicate a nearby wind slab problem. Avoid them by sticking to protected or wind-scoured areas.

    (2/2/2022) Example of wind slab and shooting cracks from the Rattlesnake.  Photo: Jeff Carty

  • Loose Dry

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

    Temperatures have stayed cold this week, and the snow has been slow to consolidate. A loose dry avalanche (slough) is the release of unconsolidated snow. They are likely today on steep, unsupported slopes where the wind hasn’t had a chance to compact. They are not usually as hazardous as slab avalanches but can carry you into terrain traps or over cliffs. Large complex terrain with steep confined areas such as a couloir could host loose dry avalanches big enough to bury or injure you.

    (1/19/2022) Example of loose dry avalanche on Little St. Joe in the Central Bitterroot.  Photo: Todd Glew

Avalanche Discussion

Yesterday was crisp, with temperatures staying below zero to the low single digits °F for much of the day. Roughly 3 to 12 inches of cold, dry snow lingers from a generous storm on Monday and Tuesday (1/31 - 2/1). This sits over various crusts formed during a January of cold nights, clear skies, and inversions. Since then, wind directions have shifted around the compass with periods of frosty north and easterly and blustery south and westerly winds. 

Near-surface facets and various surface hoar layers exist throughout the forecast area. However, they have remained relatively dormant due to the lack of cohesion or slab formation in most places. Sheltered north and east-facing areas above 6,000 are the most likely places to find persistent grains. If a slab forms atop them, they can break widely across a slope or be triggered from below or adjacent slopes. Whumpfing and collapsing are clear signs that these layers are nearby. 

Given the shifty nature of our recent winds, complexity and uncertainty are high regarding wind slab formation. Upper elevations and open locations are most susceptible to harbor reactive wind slabs. If you choose to travel in these locations, pay close attention to slope angles and thickness of the drifted snow. Areas with thick wind drifts have the potential for avalanches that are large enough to bury or injure you. Terrain traps can compound the consequences of smaller slabs. Wide-open areas could produce larger slabs. 

A small storm will bring 0 to 3 inches of fresh snow with temperatures in the upper teens to upper twenties °F today.

Ski and ride safe

 

Regioni coperte