Bollettino valanghe

West Slopes South

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

Strong winds should easily turn the new snow into firmer and thicker slabs along the lee side of ridgelines and at the base of cliffs. Blowing snow will be the most in-you-face clue to where these slabs are forming. Give steep wind loaded terrain a wide berth until the storm calms down.

Problemi valanghivi

  • Wind Slabs

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

    The storm totals might not be that impressive, but the winds could be. It’s always a little hard to say exactly how widespread or reactive newly forming wind slabs will be. Don’t overlook the obvious: blowing snow. This clue can indicate local wind patterns and help you anticipate potentially loaded slopes. With the higher wind speeds this could be well off the ridgelines or even along the sides of gullies. 

    These winds slabs might trigger more easily than normal, especially where the form over firm crust or even facets/surface hoar. Since these slabs will continue to grow through the day, if you start to see signs of reactive wind loaded pockets, they’re only going to get deeper and more widespread. 

    It will be tough to make an assessment of any wind slabs in the middle of the storm. Your best bet is to not thread the needle. Instead head for the softer snow of more sheltered terrain.

    (1/3/2025)

    Blowing snow is a clear sign of active wind loading even along this rather protected ridge. 

    Photo: Dallas Glass

Avalanche Discussion

With the storm arriving just before sunrise, there might not be much hazard first thing in the morning. However, very stormy weather will quickly cause the danger to rise. Heavy precipitation and strong winds should create poor visibility. Even after the brunt of the storm passes, showers will keep adding to the snow totals. 

We have two main questions about this storm. 1: Will the surface hoar and facets observed prior to the storm survive? This will be most likely above the rain-snow line and in more wind sheltered areas. 2: Where will the rain-snow line be when precipitation arrives? Near and below the rain-snow line could see wetter snow stick to the underlying crust. Consequently, you could see the bond between the old and new snow change quite a bit as you ascend or descend. Lower in the terrain, a transition from rain to snow and a continued cooling trend should limit the avalanche danger. 

For this storm, we think the avalanche activity will stay in the new snow. An NWAC forecaster near Crystal on Thursday noted a stronger crust on southerly slopes and at lower elevations, with a much thinner crust on shaded aspects. Recent storm layers are still visible in the upper snowpack, but shouldn’t be much of a concern with this storm. 

Prior to this storm variable travel was noted across the zone. It will take more than a few inches of snow to make the icy slopes, breakable crusts, and frozen piles of debris fully disappear.

Regioni coperte