Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Slabs of wind-drifted snow and large, fast-moving sluffs pose today's primary avalanche hazards. These can be dangerous on steep slopes where they involve more than about 8 inches of wind-blown or cohesionless snow. You can find today's best, safest riding on sheltered slopes that aren't steep enough to sluff. A week of unusually cold, blustery weather is ahead; see today's forecast discussion for the schedule of conditions updates this week. 

Avalanche problems

  • Wind Slabs

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

    Before committing to steep slopes, check for freshly-deposited slabs of wind-drifted and wind-stiffened snow. These will be most widespread in terrain that collects blowing snow or is susceptible to winds blowing across the snow surface: the tops of chutes and couloirs, the lee sides of ridges and passes, and convex rollovers. The slabs can be dangerous where they're more than 8 inches thick, and they'll be most reactive to a rider's weight on slopes steeper than about 35 degrees. Shooting cracks in dense snow are a clearcut sign of instability. You may find isolated slabs at mid-elevations, particularly in the Swan Range.

    (4/5/2022)

    A clear sign of danger: a shooting crack in wind-stiffened snow.  

    Photo: blase reardon

  • Loose Dry

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

    Step back and take a second look before diving into very steep slopes with about 8 inches of loose, dry snow. You are likely to trigger sluffs that can be dangerous where they carry you into a terrain trap or are difficult to escape. They'll be largest on slopes with long, continuously steep pitches, where they can run fast and entrain surprisingly large amounts of debris. 

    (3/10/2022)

    Low-density snow like this turn into dangerous sluffs on very steep slopes. Photo: Adam Clark

Avalanche Discussion

*This forecast is the last daily forecast for the 2021-22 season. You can find a schedule of conditions updates for the coming week below.*

Snow showers have delivered 5 to 14 inches of low-density snow to the region in the past 24 hours, with the Swan Range favored. The snowfall continues this morning, though I expect it to taper off by mid-day. We may see another round this afternoon as a cold front sweeps through the region. Winds have generally averaged below the threshold for widespread transport except at upper elevations. Gusty winds should develop this afternoon in advance of the cold front. 

From my read of weather data and limited obs, the new snow is generally cohesionless except where it's been drifted or stiffened into slabs by the wind. So I expect Wind Slabs and Loose Dry avlanches will be today's primary avalanche hazards. Storm Slab avalanches should be isolated. You can reduce your exposure to these hazards by sticking to wind-sheltered slopes less than about 35 degrees at mid elevations. 

Unusually cold, blustery weather is forecast for most of the coming week. Unusual for April, at least. Winds veer to the east and northeast tonight. Wind speeds spike Monday night and Tuesday thanks to a tightening pressure gradient between Arctic air east of the Divide and a cut-off low to the southwest. These winds will can easily drift the low-density snow into slabs in atypical locations. They're likely to harden the snow surface as they flow down the west slopes of the Whitefish and Swan Ranges. Temperatures look to be downright cold midweek, moderating by the weekend. Sadly, there's not much moisture available for snowfall in this pattern, though the Swan Range, McDonald Valley, and northern Whitefish Range may seem some locally intense snow showers.

For the week of April 11-18: Because of the unusual weather, we'll post conditions updates at least every other morning this coming week. Likely Monday, Tuesday, Thursday, and either Friday or Saturday. These will include a bottom line and discussion but no avalanche problems or danger rating.

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