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

Recent balmy weather has deteriorated this week's supportable surface crust and increased the chance of triggering a slide on deeply buried weak layers. In areas without a stout crust, choose terrain less than 35 degrees in steepness. Steer around slopes with a scoured or peppered rocky appearance where the weak layer is closer to the surface. Large cornices continue to weaken and should be given a wide berth from below and above.

Avalanche problems

  • Persistent Slabs

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

    Weather stations at mid and upper-elevations report warm temperatures overnight, which should result in a thin unsupportable surface crust on sunny aspects this morning. Therefore, locations where you can affect weak layers buried 3 to 6 feet below the surface, have increased from the previous few days. Recent warm temperatures may make these layers more reactive. Choose terrain that appears to have a deep uniform snowpack, such as areas without rocks sticking out of the snow or thin scoured slopes. If you are not on a stout supportable surface, default to slopes less than 35 degrees in steepness.

    (3/10/2021) Buried surface hoar still lurks 3 to 6 feet below the surface.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Recent cornice fall is a good reminder that a season's worth of wind deposition can ruin your day. Friday, a skier remotely triggered a large 20 foot by 15-foot chunk while another party reported large holes in cornices. Earlier in the week, a cornice fall triggered a large Persistent Slab avalanche. Continued warm weather has only exacerbated the problem. While traveling on ridgelines, stay well back from where you think the solid ground is. Gauge this location using vegetation, rocky landmarks, or scoured ground. If you choose to recreate on slopes below these behemoths, exit quickly and travel one at a time on these slopes. 

    (3/13/2021) Give the edge of ridgelines a wide berth.

Avalanche Discussion

After several days of great spring travel conditions, the reality of northwest Montana has returned. Yesterday, the surface on sunny aspects' was moderately frozen in the morning but quickly softened as temperatures spiked. While touring, I ran into a friend who did a couple of laps on an exposed southeast face in the morning. Run one was firm, with run two being perfect corn.  She remarked that conditions were changing fast, which I noticed as the surface deteriorated and allowed me to sink boot top, or more, deep.

The supportable surface crust earlier in the week allowed us to trim the location of the Persistent Slab problem from all aspects to just the shady slopes at upper elevations where there was no crust. We felt confident that humans and their machines couldn't affect buried weak layers in areas harboring a stout supportable surface. Weather stations at mid and upper elevations remained warm overnight resulting in a weak surface refreeze. Today's warm temperatures and sunshine should break this eggshell crust down quickly. Without a stout supportable surface crust, we have expanded the Persistent Slab problem to locations where it was located a week ago; mid and upper-elevations around the compass.

We do not expect natural wet loose activity but anticipate that riders may initiate small sluffs and rollerballs on steep slopes. If you find yourself in larger terrain, be mindful of how a small sluff can easily sweep you off your feet or machine. Avoid traveling above terrain traps where even a small slide can pile up deep. If you or your machine are sinking into the snow more than a few inches, it would be wise to move to a shadier aspect for a safer and higher quality experience.

Glide cracks (Example one, Example two) continue to open across our area. These unpredictable brown frowns can either fail catastrophically or melt in place. Recent warm temperatures and sunshine have allowed the season's snowpack to start to move downhill. Providing you can spot these ahead of time, they are an easy problem to manage. Staying off and out from under these cracks is the only surefire way to avoid this problem.

Check out our most recent weekly avalanche and snowpack update in the media gallery or here.

 

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