Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 5 years ago.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

Highlights

With lingering avalanche hazards at all elevations, careful terrain choices and safe riding practices remain important. You can minimize your chances of surprises by riding planar or concave slopes less than 35 degrees that are sheltered from the wind. Similarly, you can minimize the consequences of surprises by riding one at a time with a full set of avalanche rescue gear.

Avalanche problems

  • Persistent Slabs

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

    The most likely way to find trouble today is party skiing  steep slopes that face north, northeast, or east near ridgelines in the southern Whitefish Range. In this terrain, you can trigger slabs that break six to 18 inches deep, producing enough debris to slam someone into a tree or bury them in a tree well. Simple steps can limit the consequences if you get surprised: ride one at a time, keep your partners in sight, and carry avalanche rescue gear even on short trips outside the resort boundary. Outside the southern Whitefish Range, you can trigger similar slabs on facets near crusts. Stack the deck in your favor by riding planar or concave slopes with clean runouts - no gullies, trees, or rocks below. If you feel whumpfing collapses or see shooting cracks, avoid traveling below steep slopes. 

    (2/7/2022)

     A rider stomped along a cornice/rollover and set off a decent sized slide, 6-12" crown, approx 100' wide. North-northeast aspect, 6380 feet in the Southern Whitefish Range on 2/7 

    Photo: Public

  • Wind Slabs

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

    Slabs of recenty-drifted snow pose a lingering hazard at upper elevations. They can break one to two feet deep, and you can trigger them from thin spots near rocks, from their edges, or from below, as you're climbing towards a ridgeline. The most straightforward way to address this unpredictability is to avoid terrain likely to harbor them: the tops of steep chutes and couloirs, crossloaded gullies, and steep slopes below corniced ridges. This terrain is no place to dawdle; falling cornices can trigger larger slabs on slopes well below ridges.

  • Loose Wet

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

    Wet snow avalanches are possible on very steep slopes where crusts have softened or the snow is getting wet for the first time. Avoid being on or below slopes steeper than about 40 degrees where you see fresh rollerballs or sticky snow is clumping to the bottom of your board, skis, or machine. 

    (2/6/2022)

    Roller balls on a steep mid-elevations slope. These indicate a person on the same slope might be able to trigger a small, wet loose avalanche.

    Photo: Cam Johnson

Avalanche Discussion

What do you do with a problem like the surface hoar in the southern Whitefish Range? In the past 8 days, riders have triggered a series of slides on slopes that broke on well-developed surface hoar about a foot below the surface on north-, northeast-, and east-facing slopes in this corner of the region. One left a rider pinned to a tree and lucky to be uninjured. The most recent occurred Monday. Yet tests on nearby slopes are not producing propagation, even when the grey stripe is obvious.  And most parties in the area aren't reporting collapses or cracking. The most straightforward answer? Avoid terrain with similar characteristics, or at least approach it carefully, testing with hand pits and slope cuts before commiting. And most importantly, riding with avalanche rescue gear and keeping your partners in sight, so any surprises have minimal consequences. One note - the reported slides were triggered on slopes near or just below ridge crests, where wind-blown snow has likely stiffened the slabs. Mid-slope convex rollovers are another likely trigger point.

Outside of the southern Whitefish Range, the primary concerns are layers of facets near melt-freeze crusts. These layers are also buried six to 18 inches deep. They're widespread, and people have reported collapses and some propagating failures in large column tests in the Flathead Range. We've had one report of a possible triggered slide outside the southern Whitefish Range. This occurred in the northern Whitefish Range and may have been machine-triggered. That's not enough evidence to write this structure off. Not for me, anyway. I'm still looking for ascent routes free of overhead hazard and on slopes less than 30 degrees, and descending planar or concave slopes that aren't above terrain traps like gullies. Small efforts that may keep any surprises small and manageable. 

The winds... Upper elevations saw winds strong enough to peel paint off a wall early this week. Plumes of blowing snow were obvious at ridges, and the winds even worked into usually sheltered terrain, hardening snow surfaces. It also left a lingering hazard of hard slabs on steep, top-loaded and crossloaded slopes. It's hard to distinguish these from harmless wind crusts without digging. Avoiding steep terrain likely to harbor these slabs is more straightforward. Many freshly-formed cornices may sag and break in the warm weather; the falling debris can trigger hard slabs on slopes below, so scurry through ruouts below ridges with cantilevered cornices.

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