Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Thu
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

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.  

Problemi valanghivi

  • Persistent Slabs

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

    This weekend’s storm deposited up to 1 foot of snowfall on faceted snow from earlier this month. Weak layers formed during the January drought are buried more deeply (2 to 3 feet). While these layers are widespread, you are most likely to trigger an avalanche in isolated areas where February’s snowfall has settled into a cohesive slab or has been stiffened by wind or sun.

    Be leery of slopes harboring stiff snow above weak layers. 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 more reliable methods to confirm if a slab has formed.  

    Signs of instability have been concentrated in the Whitefish Range, where multiple groups continue to report collapsing (whumpfing), shooting cracks, and a remotely-triggered avalanche. We have fewer reports of these signs of instability from our other zones.

    (2/13/2025)

    A large natural avalanche triggered by a natural cornice fall from the ridge above. The intial debris stepped down to older weak layers as it ran down slope. SS-NC-D2.5R2-O

    Photo: Flathead Avalanche Center

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    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 it is difficult for a rider to escape their sluff.

    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. Also keep in mind that surface slides have the potential to trigger a larger avalanche on a buried weak layer.

    Solar radiation can cause natural sluffing on steep and rocky southerly slopes. Tuesday’s sunshine may have already worked over slopes that received direct sunshine. Keep an eye out for lingering natural activity on southerly slopes that have not sluffed yet.

    (1/27/2025)

    One small (D1) loose dry avalanche in steep terrain. Sluff was small and inconsequential. 

    Photo: Cam Johnson

Avalanche Discussion

Some new snow, sunshine, and warmer temperatures will aid in slab formation above the January weak layers.  Don’t let exceptional riding lure you onto steep slopes without first checking to see if there is a slab on top of weak snow.

Here are some settled storm totals and SWE (Snow Water Equivalent) from Friday 2/14 to Monday 2/17. Keep in mind that these likely understate the actual snowfall due to settlement:

  •  Stahl (Northern Whitefish Range) = 8 inches (1.5 SWE)
  •  WMR (Southern Whitefish Range) = 8 inches
  • Flattop (Glacier National Park)= 5 inches (0.6 SWE)
  • Tunnel (Flathead Range) = 11 inches
  • Noisy (Swan Range) = 11inches (1.5 SWE)

The bulk of the storm was focused south of the advisory area. Yesterday, I cleared 2 feet of new snow off of several roofs in the Swan Valley. If you are traveling south of Swan Lake, be prepared to find deeper snow and higher danger. Avalanches in the new snow are becoming less likely, but could still fail on the old snow surface or deeper down on a buried weak layer. Persistent slabs avalanches may become more reactive in the next few days as temperatures warm. 

Expect the danger to spike this weekend 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.

Upcoming Events: Check out our calendar and sign up now!

  • February 20-22nd: Avalanche Safety: Introduction to Avalanches Human Powered for Skiers and Snowboarders - register here
  • Feb 26th - State of our Snowpack Presentation at 7pm for Pint Night at Blackstar with donations going to Flathead Avalanche! 

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