Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

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

In sintesi

The heat wave has ended, and the hazard of a large natural or human-triggered avalanche on a buried weak layer is decreasing. On shady slopes, stick to locations with a supportable crust to minimize your chance of triggering one of these beasts. Fresh snow and wind continue to form thin slabs of wind-drifted snow at upper elevations, best managed by choosing sheltered terrain.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Cooling temperatures are decreasing the odds of a natural or human-triggered avalanche on a buried layer of surface hoar found 2-5' below the surface. This week's meltwater may still be moving through the snowpack, so the likelihood of a natural avalanche is uncertain. 

    Several large to very large slides failed on the January Drought Layer over the past few days on slopes facing north to east, confirming that this problem remains our primary concern. Surprisingly, snowpits on the north side of the compass continue to show the tell-tale obvious grey stripe two months after formation. 

    A surface crust began forming yesterday morning at mid and upper-elevations and will limit the stress a rider puts on the buried weak layer. If you plan to ride NW-NE-SE slopes, check that this layer is supportable. If not, default back to low-angle terrain not connected to steep slopes or travel on S-SW-W slopes where this problem does not exist.

     

    (3/19/2026)

    Very Large avalanche on Sixmile Mountain in the Swan Range.  Estimated to have run on 3/19. 7300 feet, North.

    Photo: Chris Gotschalk

  • Wind Slabs

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

    Saturday's precipitation likely resulted in 6-12 inches of fresh snow across the Swan and Flathead Ranges above 6500 feet. Blustery southwest winds have drifted this into thin slabs downwind of ridgelines, saddles, and summits. In places, these features may have formed on a crust that inhibits bonding and increases the likelihood of triggering. A small surface slide could trigger a much larger slide as described in the Persistent Slab problem above.

    Today's blowing snow will point in the direction these slabs are forming. A textured or scalloped surface indicates that the wind has been at work, and slabs may be found nearby.

    Cracking beneath your feet or machine indicates you have found a slab. Choose terrain sheltered from the wind for a safer and more enjoyable experience.

    (2/26/2026)

    Today's blowing snow will likely result in fresh slab formation. These should be small and relatively easy to avoid. 

    Photo: Guy Zoellner

Avalanche Discussion

A welcome cold front dropped temperatures below freezing early Saturday morning, and they've remained there for about 24-30 hours. This follows several days when the temperature stayed above freezing, including two days where highs reached the upper 30s to low 40s at stations above 6500 feet.  

This week's warming and rain resulted in wet loose avalanches, wet slabs, persistent slabs, and cornice fall. A drop in temperatures will gradually lock up the snow surface and reduce meltwater production, leading to a decline in natural avalanche activity. 

After 33 consecutive days of a danger rating of Considerable or higher, we dropped the hazard to Moderate in the Whitefish and Swan Range. We are keeping the danger elevated for one more day in the Flathead due to more recent precipitation and warmer temperatures.

The balmy weather took a toll on the snowpack, with the Tunnel Ridge snow depth dropping 21 inches since Monday. The 22 inches that fell on the valley floor in John F Stevens last week have melted away. If you have driven Highway 2 west of Columbia Falls, you may have noticed that the Flathead River is big and brown. The Middle Fork River will peak today at 13,400 cfs, nearly nine times greater than last weekend. The North Fork River crested at 12,000 cfs on Saturday, well above last weeks 1500 cfs.

Despite the crazy weather, the three mid-elevation SNOTEL stations in Flathead County still report median values of 89-99%. Low-elevation SNOTELs are reporting totals you would expect, 45-53%.

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