Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The simplest way to enjoy the pre-holiday delivery of recent snow is to stick to slopes less than about 35 degrees. If you step out into steeper terrain, minimize the dangers of triggered slides involving the recent snow by riding terrain where you can escape moving debris or where moving debris won't carry you into terrain that increases the chances of being buried or injured. 

Avalanche problems

  • Storm Slabs

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

    On upper elevation slopes where dense snow rests on softer snow, you can trigger soft slabs that break in the new and recent snow. Due to variable snowfall totals, the slabs may range from 6 to 24 inches thick. They are more likely to be dangerous where steep start zones funnel into confined paths or run over or into terrain traps, like rock bands, gullies, or trees. These slabs will usually give themselves away by cracking around your skis, board, or machines. Active tests can help you identify where slabs exist. These tests include stomping or cutting steep, low-consequences test slopes and cornice drops. This problem is isolated at mid-elevations.

    (12/14/2021)

    Riders in the Swan Range found debris from a small storm slab that released naturally on a west aspect above 6,500 feet.

    Photo: Peitzsch

  • Loose Dry

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

    On very steep slopes where soft snow sits over firmer snow, you can trigger sluffs that run far and fast enough to be dangerous. Look for - and avoid - start zones 40 degrees or steeper where the track below stays continuosly steep. Sluff on slopes like these can entrain enough surface snow to be dangerous, or gouge into the recent snow and pull dangerous amounts of debris with them. It can be hard to escape these in confined terrain - like chutes and couloirs. Small sluffs can have outsized consequences if they carry you over a cliff or into trees, rocks, or gullies. This hazard exists on isolated slopes at mid-elevations.

    (12/14/2021)

    Sluffs, like this one, are possible where cohesionless surface snow pours down steep slopes. The sluff in this picture did not entrain much snow and was harmless in size.

    Photo: Reardon

Avalanche Discussion

Today's a day to have your inclinometer handy and to use it regularly. Or, if you want to keep it simple, avoid slopes steeper than about 35 degrees. That's because slope angle is the primary factor influencing the likelihood of triggering avalanches you today. And the danger posed by triggered slides will increase in more complex terrain: slopes that are confined, have a continuously steep pitch, or are above terrain traps. 

The region saw an additional 2 to 8 inches of low-density snow Tuesday, with little wind. We had reports of a few small, mostly harmless avalanches: a natural soft slab avalanche in Noisy Basin and small but eager-to-run sluffs in and around Whitefish Mountain Resort. The new snow will have settled and consolidated a little overnight. 

Rider and forecaster observations over the past week have consistently described a snowpack that's mostly stable with few, if any, distinct failure planes. As a general image, picture 35 to 100 cm (that's one to 3+ feet) of snow that's fallen since Dec. 3. That snow gets progressively harder with depth and sits above a very hard crust or ice mass from the not-so-cold November rain. This crust extends well above 7000 feet and is unlikely to collapse under the weight of a skier or machine. The only reports of natural avalanches are from very steep, northerly terrain near Red Meadow Pass, in the Whitefish Range; these occurred during the weekend's storm.  That evidence - or lack of evidence - indicates there's little hazard involving slides breaking on old snow deep in the snowpack or near the ground in most of the region. The exception would be the highest terrain in the region, particularly in the Flathead Range and Glacier National Park, where it didn't rain or where powerful winds have left hard wind slabs in steep leeward terrain. 

So today's avalanche hazard involves new and recent snow. Avalanche basics apply. Stick to lower angled slopes to decrease your chances of triggering a slide. Or if you accept a higher risk of triggering a slide, stick to lower consequences terrain - open slopes with easy escapes and runouts clear of things that would hurt if you hit them. Use active tests to identify where slabs exist and are reactive to the weight of you or your machine. And let us know what you find.

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