Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 4 years ago.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

Highlights

Dangerous conditions exist on and below steep slopes across the forecast region. Riders are likely to trigger slabs 1 to 3 feet thick that break on buried weak layers near the ground. Getting caught in even a small slide can have nasty consequences if you get raked over rocks and stumps and tumbled through much-harder-than-they-look Christmas trees. Stick to slopes less than 30 degrees that aren't below steep start zones or above terrain traps. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Dangerous conditions exist on and below steep slopes where this week's storm has loaded old, weak snow with slabs 1 to 2 feet thick. Whumpfing collapses, shooting cracks, and fresh avalanches are flashing signs that this structure is present and reactive. Stick to slopes less than 30 degrees that aren't in the runouts of steeper start zones. Small avalanches can have outsized consequences if they tumble you through trees and over rocks, stumps, and other things harder than your body. 

    A small, skier-triggered slab above weak faceted snow. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    This week's storm dropped copious amounts of soft, low-density snow at upper elevations. That snow is readily drifted by the gusty southwesterly winds that started early Friday morning and will continue today. Look for soft slabs of wind-blown snow on the lee sides of ridges and saddles, and crossloaded into gullies and chutes. These slabs will feel denser than snow on sheltered slopes and may crack around your boards or machine. These slabs can break 1 to 3 feet deep; the moving debris can in turn trigger avalanches that break on weak layers buried near the ground, making for larger, more dangerous avalanches. You can minimize your exposure to this hazard by sticking to slopes less than 35 degrees or to slopes sheltered from the wind.

Avalanche Discussion

We're not in MT anymore, Toto. That is, conditions aren't typical for this time of year. To us two-legged plank- and track-riding humanoids, it seems like we have lots of snow. The snowpack, however, is responding to the past month's weather like a shallow snowpack. Cold temperatures in the middle of November weakened the snow on the ground, and storms since Nov. 21 have incrementally loaded that weak snow. This week's storm added another 10 to 20 inches to the slab above the weak layers, creating dangerous conditions on and below steep slopes. It's a pattern and structure more typical of central Idaho or Colorado. 

Big picture evidence that these conditions exist?

  • 17 of 19 observations since Nov. 21 have included reports of whumpfing collapses or shooting cracks.
  • 10 of the 19 observations have reported natural or triggered avalanches, with several reports of remotely-triggered slides.
  • We've had 3 reports of triggered slides and near misses since Sunday. That's a lot for this region, particularly when access is still limited. The most recent occurred Friday morning, when a rider narrowly escaped a slab he remotely triggered. 

Getting more precise, reports so far indicate this structure is widespread at mid-elevations (above 5000 feet) across the forecast region. The weak layer consists of soft, faceted snow; on many slopes it's associated with 1 or 2 crusts. The crusts seem to fade between 6000 and 6500 feet. So far, reports aren't describing much surface hoar mixed into this layer. It's not clear how widespread the mid-November facets are at upper elevations, due to a lack of observations. 

Two factors might make accidents involving this Persistent Slab structure more likely. The first is that it's unusual, so our usual habits might not be sufficient to keep us out of trouble. The second is that the easiest access to the backcountry is to familiar places that we don't associate with avalanche danger. Like, say, our favorite runs at Whitefish Mountain Resort, which are no different than backcountry slopes right now due to lack of avalanche mitigation. Or the small, steep play areas without previous snowmachine traffic. 2 of the 3 incidents this week occurred in those situations. 

So travel with a mindset that conditions are unusual and unpredictable. Check the condition of your rescue gear and carry all of it (beacon, shovel, probe, and airbag). Look above you for steep slides that could clobber you with debris if triggered from below. Look below you for terrain and trauma traps. 

Check out our new Observation View page. It highlights signs of instability and allows you to filter by date or zone, so you can pull out reports relevant to your objectives. We've updated our observation submission page as well. 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 vague or specific as you want. 

Preseason restrictions on uphill travel are in effect at Whitefish Mountain Resort. 

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