Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
View on map

Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map
Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Conditions remain dangerous due to continued wind transport, recent snow, and weak layers buried deep in the snowpack. To minimize your risk, limit your travel on and below steep, wind-drifted slopes. Avalanches can break wider and run longer than expected.

The upper McDonald Valley received significantly more snow and the avalanche danger may be higher in central Glacier National Park.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3

    Over the past 5 days, moderate to strong southwesterly winds have drifted snow onto leeward slopes along ridgelines and cross-loaded gullies. Winds peaked yesterday (Thursday) afternoon but are still sufficient to continue building slabs today. Both older and freshly-formed slabs remain sensitive to the weight of a rider. 

    Scalloped snow surfaces and dune-shaped features are visual indicators of wind-drifted snow. Slabs may range from soft to hard. Soft slabs may crack around your feet or machine to warn you of their instability.  Hard slabs will not do this until it's too late. If your skis, board, or machine start to ride on top of a stiff, hollow-sounding surface you've likely found a hard slab.

    For the best and safest riding, seek out sheltered slopes.  Recognize that isolated wind-sheltered slopes may still harbor lingering instability in the storm snow. Opt for low-angle terrain where you find 8 or more inches of recent snow. 

    Keep in mind that even a small slide can step down to a deeper weak layer and result in a larger, more destructive avalanche as described in the Persistent Slab problem below.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Steep, shaded slopes at mid and upper elevations remain particularly dangerous. In this terrain, slides can break 2-4 feet deep on a layer of weak, faceted snow. This layer is often located several inches above a stout crust formed in early February. It has been difficult to identify in snowpits and has yielded mixed results in stability tests.

    The Flathead Range has seen the most activity on this layer. Large natural avalanches ran on this layer as recently as  Thursday in John F. Stevens Canyon. Human-triggered avalanches during the President's  Day weekend resulted in several accidents and near-misses in the Marion Lake area. The structure has been reported across the region and was the cause of a fatality in the Canadian reaches of the North Fork of the Flathead River on Feb. 24.

    Wind will continue to drift recent snow onto this weak structure. This added stress may result in natural avalanches or could increase the chance of human triggering. Slabs can break well above you, wrap around terrain features, and will be difficult if not impossible to escape. They can also be triggered remotely or sympathetically, from below or from adjacent slopes. 

    (2/29/2024) February 29th, 2024: Crown of large hard slab avalanche that failed sometime last night on the north face of Devils Hump. Photo: Adam Clark

Avalanche Discussion

Yesterday (Thursday) was pretty wild: intense, buffeting wind and natural cornice fall on the ridge top, and 50*F with sticky snow down low. Somewhere in between, though, there’s good honest riding in wind-sheltered terrain.

Today should be one step closer to normal. Most stations are reporting seasonable temperatures, decreasing winds, and a trace of precipitation overnight. The one notable exception is in central Glacier National Park, where Flattop Mountain picked up another 1.3 inches of SWE in the last 24 hours. That totals 2.5 inches of water and 14+ inches of snow in 48 hours for that location. Slabs in the upper McDonald Valley will be thicker. 

Though the weather moderated some, the danger remains elevated. Winds are still sufficient to build slabs and add stress to buried weak layers. Yesterday (Thursday), BNSF Avalanche Safety reported a handful of large to very large hard slabs on wind-loaded slopes in John F Stevens Canyon. Several likely failed on the uncooperative facet layer near the early-February Crust. This layer continues to give mixed results in pit tests. It may not look like much, but for the time being, it still deserves some respect. When in doubt, opt for simple, low-angle terrain.

Regions covered