Bollettino valanghe

Whitefish Range

Flathead Avalanche Center
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Pericolo valanghe

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

In sintesi

Strong, shifting winds have formed drifts of snow on all aspects and elevations. You may find them along ridges, in open bowls, or well downslope in areas that are typically sheltered from the wind. Signs of wind-affected surfaces may be hidden by recent snowfall. Visible cracks or audible collapses are signs of unstable snow that should steer you toward lower-angled slopes.

Problemi valanghivi

  • Wind Slabs

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

    Yesterday (Wednesday), winds shifted to more prevailing directions (souht through west-northwest) and increased throughout the day, building fresh slabs on typical leeward ( NW-N-NE-E-SE-S) slopes at middle and upper elevations. Thin soft slabs were easily triggered on slopes down-wind from exposed ridges. Older, but still problematic, slabs may exist on a typically windward slopes due to recent northeasterly winds. 

    In some areas, the typical signs of wind-affected snow - scalloped surfaces or dune-shaped features - may be hidden by more recent snow fall under calm conditions. Probe around with a ski pole or dig a quick hand pit to verify what's under your feet. 

    Recent and wind-drifted snow continues to load a weak layer of facets and faceted crusts formed during the January dry spell. It may be possible to remotely trigger avalanches from low-angle or flat terrain above, below, or to the side of steep slopes. A large (D2) natural avalanche in John F Steven Canyon likely failed on this layer sometime Tuesday night or Wednesday morning. 

     

     

     

     

     

     

     

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    (2/5/2025)

    Intentionally triggered small (D1) soft slab on a wind-loaded NE slope at 6900'

    Photo: Flathead Avalanche Center

Avalanche Discussion

Observations have been sparse over the last 3 days due to blustery and bitterly cold conditions.  A handful of reports from yesterday (Wednesday) featured:

Precipitation totals and settled snow increases since 1/31 are:

  • Noisy Basin (Swan Range) = 1.8" SWE, 12" snow
  • Stahl Peak (Northern Whitefish Range) = 1.6" SWE, 10" snow
  • Flattop Mountain (GNP) = 2.0" SWE, 12" snow

Overall, we have not yet seen widespread activity on the well-documented weak snow surface from January.  This may partly be due to limited visibility and observations. More importantly, it may be that we have not yet reached the tipping point for this weak layer.

Areas to the north, west and south of us have received more snow (2+ feet) on a similarly weak structure and have (unsurprisingly) seen more avalanche activity (examples: Fernie, Selkirks, Sawtooth). The reported avalanche from JFS canyon occurred in wind-loaded terrain and had an estimated crown height of 3+ feet.  With more snow showers in the forecast, it is possible we will continue to incrementally load this layer until it becomes reactive.

Skies are forecasted to clear throughout the day.  If you get some decent visibility, scan the lanscape for crowns and debris piles. These observations will help us determine if we are approaching, at, or past the tipping point.

 

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