Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
Voir sur la carte

Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 7 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

While the odds of a rider triggering a large avalanche on a buried weak layer are decreasing, that hazard remains our primary concern. Traveling on slopes with a strong, supportable surface crust will minimize your chance of tangling with one of these beasts. In locations where the crust does not support your weight, choose lower-angle terrain to reduce your risk.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    The chance of a natural or human-triggered slide on a weak layer buried 1-3 feet deep continues to trend down. Recent dry conditions and a hard surface crust contribute to, but have not eliminated, this problem. 

    The conditions for a Persistent Slab avalanche are not present on all slopes, and it's challenging to determine where they are or aren't. The safest bet is to assume that the troublesome slab/weak-layer/crust combination exists on all slopes. You will likely not experience obvious signs of instability—snowpack collapsing or cracks shooting out from your skis or sled—before triggering an avalanche. The resulting slides may propagate farther than expected, triggering a large avalanche.

    Choosing slopes with a supportable surface crust will decrease the odds of impacting this layer. Defaulting to lower-angle terrain not connected to a steeper overhead hazard will minimize your risk.

    (1/16/2026)

    A large, natural slab avalanche on Slippery Bill Mountain in the Skyland area. (7300' - NE - D3). This likely failed on a buried weak layer.

    Photo: Michael Reavis

Avalanche Discussion

The last reported human-triggered avalanche on a buried weak layer occurred on January 10. Natural activity has also tapered off, with the last known slides occurring several days later. Our recent unusual weather pattern is partly responsible for this decline, as the last measurable snowfall occurred around January 8, and wind transport ceased several days after that. Above-average temperatures and sunny skies left a melt-freeze crust on most aspects at mid-elevations and on many upper-elevation slopes. Since Thursday, cool temperatures have kept the snow surface locked up in many locations.

Due to the strong surface crust found on sunny middle-elevation slopes, we have trimmed the distribution of the Persistent Slab problem from SW-S-SE terrain below 6500 feet. The crust caps the surface snow and limits the stress you or your machine exerts on the weak layer. 

With less-than-stellar riding conditions, public observations have tapered off. Yesterday (Saturday), riders explored the upper elevations of the Flathead Range in search of soft snow, which appears to be in short supply (observation, observation). Mike and I enjoyed a day at WMR, teaching a FOFAC avalanche class to a fun and engaging group. At around 6500 feet, we found a supportable 5cm surface crust on sunny slopes, and an eggshell-thick crust on shaded slopes, with dry snow beneath.

Education offerings:

Human-powered partner rescue clinic, January 24. Find out more details here. 

Ladies' human-powered Intro to Avalanches January 29 and 31. Get more details here.

 

 

 

 

Régions couvertes