Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You can trigger an avalanche on weak layers buried 1 to 3 feet deep. Slides will be larger and more sensitive where wind has drifted snow. Signs of instability - like cracking or collapsing - should steer you away from steep slopes. Sluffs may occur on very steep slopes and can trigger a larger avalanche deeper in the snowpack.  

Avalanche problems

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    You can trigger sluffs in the recent snow. Loose Dry avalanches are most common on very steep slopes. These may grow larger as they gouge into older layers of facets. You are most likely to get caught in confined or long-running chutes where you are unable to escape to the sides.

    Even small sluffs can knock you off your line, into the bushes, over a cliff, or bury you deeply in a gully or creek bed. Keep in mind that surface slides have the potential to trigger a larger avalanche on a buried weak layer.

    (2/19/2025)

    Getting caught in a sluff above these cliffs, or in one of these chutes could have devasting consequences.

     Photo: Michael Reavis

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    Weak layers of faceted snow and surface hoar are buried 1 to 3 feet deep. You are most likely to trigger a slab avalanche where recent snowfall has been stiffened by wind or sun. You might see or feel obvious signs of cohesive slabs at the surface (i.e. wind-textured snow, or cracking). In some locations, slabs are covered by recent low-density snow. Probing or digging are reliable methods to confirm if a slab has formed.  

    Today's increasing southwest winds will continue to load weak layers while building thin surface slabs. Steer away from likely trigger points like convex roll-overs or slopes peppered with rocks. Natural and human triggered avalanches occured during the last 3 days in zones north and south of the advisory area. Observations from the Whitefish Range continue to feature buried surface hoar and obvious signs of instability like "whumpfing" collapses. 

    (2/13/2025) D1.5 slide triggered on eastern aspect at 6600ft. 35 degree slope angle.

Avalanche Discussion

If you notice blowing snow today, you can expect thin wind slabs to develop along exposed ridges and in open bowls above 6500'. Look for the usual signals like scalloped surfaces, or dune-shaped features.

I made a couple small but notable tweaks to the forecast this morning:

  1. I bumped the likelihood for Persistent Slab from unlikely to possible for the Swan and Whitefish Ranges. Yesterday's high temperatures were among the warmest we've seen since January. Temperatures are forecasted to remain 20 to 30* F.  Warmer temperatures will promote settling in the snowpack and could result in slabs that are more widespread and sensitive. Buried surface hoar has been found in both ranges. The Whitefish range has been a hot bet for "whumpfing" collapses and propagating pit tests while the Swan range was favored by recent snowfall. The problem remains unlikely in the Flathead Range and GNP.  Observations from yesterday documented widespread sluffing but, but these did not trigger any avalanches on buried weak layers. 
  2. I removed W-SW-S aspects from the Loose Dry problem as these slopes have been worked over by the solar radiation during the last two days and in some cases are capped with a melt-freeze crust. That being said, if you're on traveling on these aspects and find light, dry snow instead of a crust, you can expect some sluffing on very steep pitches.

South of the advisory area, a few large to very large slab avalanches ran naturally during and after the most recent storm. To the North, skier- and snowmobile-triggered D1.5 slab avalanches have been reported near Fernie, BC during the last 3 days. These recent avalanches are reminders of the lurking danger of weak layers in our snowpack. These slides all occurred on rocky, wind-affected slopes.

Expect the danger to spike Sunday into Monday as an Atmospheric River targets NW Montana. The rain/snow line is forecasted to rise above 5000 feet with the potential for 1 to 2 inches of SWE.

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