Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Dangerous conditions exist on and below steep slopes at upper elevations. You can trigger large, dangerous avalanches from below or from adjacent slopes. These can break 1 to 3 feet deep. You'll find similar conditions on some mid-elevation slopes, though they are less widespread. Limit yourself to simple terrain: low-angled slopes sheltered from the wind that aren't under steep start zones or above terrain traps.

Avalanche problems

  • Persistent Slabs

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

    After 5 consecutive days of natural and rider-triggered avalanches, persistent slabs remain dangerous . The troubles begin at about 5000 feet and grow more widespread the higher you go. Most of the slides have occurred on north to east to southeast aspects. Gusty winds and 3 to 9 inches of new snow Tuesday have compounded the problem by thickening slabs above weak layers of facets and surface hoar. These slabs are now 1 to 3 feet thick.They are denser, larger, and more reactive where wind have stiffened the surface. You can trigger them from adjacent slopes, or from below. Heed obvious red flags like shooting cracks or collapsing in the snow around you. Use extra caution as you gain elevation. Default to planar slopes less than about 35 degrees. Avoid complex terrain and slopes with terrain traps below.

    (2/1/2021) Avalanche Incident on Paola Ridge

Avalanche Discussion

Over the last five days, rider-triggered, remotely-triggered, and natural persistent slab avalanches have run on steep slopes across the region. Most of these avalanches occurred on north to east to southeast aspects above about 5,500 feet where wind and temperatures have stiffened the newer snow at the surface. The weak layers responsible are surface hoar and facets buried 1 to 2.5 feet deep. The sliding surface of these avalanches has generally been the slick crust buried on January 13th, or old wind board at elevations higher than that crust reaches.

On Tuesday, 3 to 9 inches of new snow fell across the region. Observers in the Swan Range and the Lake McDonald area reported loading rates of greater than an inch per hour. The snow line was around 4,500 feet with rain soaking the snowpack at lower elevations. The Tunnel Ridge, Flattop, and Shed 7 (John Stevens Canyon) weather stations reported the most precipitation with 0.5-1 inch of new water. Winds remained at snow-blowing speeds overnight. Ordinarily that kind of loading would prompt me to warn you about slides breaking where the new snow meets the old. But with the persistent weak layers so reactive and widespread, I expect any true storm slabs to be isolated. Most smaller avalanches you can trigger in the new snow have the potential to step down and slide on the 1/13 crust.

The snowpack at lower elevations has likely refrozen. Watch for overhead hazards if you cross under long-running avalanche paths. Ascending on low-angled, sheltered terrain where you can assess the danger before exposing yourself is a safer way to travel.

Regions covered