Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Dangerous avalanche conditions will develop through the day. Six to 10 inches of new snow may fall with temperatures dropping to -30 degrees Farenheight overnight. Weak layers buried near the base of the snowpack continue to show signs that it is possible to trigger a large avalanche failing 1 to 4 feet thick. Any triggered avalanche may run long distances and entrain a surprising amount of snow. Bundle up and keep it simple today by sticking to low-angled slopes free of overhead hazards.

Avalanche problems

  • Storm Slabs

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

    There is a smorgasbord of new snow avalanche problems out there today. We have lumped Storm Slab, Loose Dry, and Wind Slab into one problem. Manage them all the same. Keep slope angles less than 30 degrees, and be aware of the terrain above you. Any triggered slides may run long distances and entrain a dangerous amount of snow. Avalanches may fail naturally today. Shooting cracks, blowing snow, and point releases coming from steep terrain are all signs to give avalanche-prone slopes a wide margin today.

    (12/18/2022)

    An overproducing storm formed thin soft slabs in the new snow by day's end. 

    Photo: Erich Peitzsch

  • Persistent Slabs

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

    Whumpfing collapses and unstable snowpit tests show that weak layers buried near the bottom of the snowpack may still produce an avalanche that wipes out most of the season's snow. A triggered avalanche in the new snow may step down and cause a large, dangerous avalanche. Manage this problem with simple terrain selection. Stick to slopes with angles less than 30 degrees while steering clear of overhead hazards. Avoid steep breakovers and areas where the snowpack may be thin and rocky during your hunt for lower-angled terrain. 

    (12/19/2022)

    This Propagation Saw test released a slab before the cut was half the length of the block. That result indicates that the snow structure is still capable of propagating a failure. 

Avalanche Discussion

The primary avalanche problems you will likely encounter today will be in the new and recent snow. Today is a day that a “New Snow” avalanche problem would be useful. This is because it is likely you may encounter Loose Dry, Storm Slab, and Wind Slab all in a single outing. In sheltered terrain, expect to encounter Loose dry avalanches, while Wind Slabs may be more common near ridgelines. Storm Slabs may become more likely as the day progresses and snowfall accumulates.

A complex day calls for simple terrain selection. Keep slope angles lower than you may have in the past few weeks to offer yourself a wider margin for error.  A triggered slide may entrain a large amount of snow as it comes ripping down the mountain and be large enough to bury and kill a person. Avoid being on or under avalanche terrain today.

Cold north and east winds will channel through valleys as moist westerly flow will come swooping in overhead. Hopefully, this overriding event plays out and we see snow totals reaching 6 to 18 inches by Wednesday afternoon. Winds will shift to the north and east this evening. This shift in wind direction will cause temperatures to plummet throughout the forecast area. Air temperatures may reach -30 F with wind chills nearing -60 F!

Since Saturday, the forecast region has picked up anywhere from 8 inches to 2 feet of new snow. Observations are summarized by sluffing snow in steep terrain, developing storm slabs, and reactive slabs anywhere the wind has drifted snow. High-quality powder riding on lower-angled slopes is also a common theme. Observers who continue to poke and prod persistent weak layers near the bottom of the snowpack continue to find unstable scores in snowpit tests. Riders felt audible collapses on Saturday and Monday.

Training: Now's a great time to hone your companion rescue skills. Transceiver parks are open at Whitefish Mountain Resort, one at the summit and one adjacent to Grey Wolf. Both are accessible to snowmachines. You can get more details about training and education opportunities events on our events calendar.

Observations - Thanks to everyone who's been utilizing our new observation submission page. Try it out and help your community by sharing what you see in the backcountry. The form requires you to fill out the location fields and put a dot on a map. Be as specific or vague as you want. Our new Observation View page highlights signs of instability and allows you to filter by date or zone to pull out reports relevant to your objectives.

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