Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

The weekend's new snow can pose a hazard on steep slopes, primarily at upper elevations. More new and drifted snow accumulated in this terrain, making triggered sluffs or small, thin slabs harder to escape. Avoid steep, confined slopes above gullies, dense brush, trees, rocks, and other features that can increase your chances of being buried or injured if you're surprised.

Avalanche problems

  • Loose Dry

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

    While you can trigger sluffs of new snow on most steep slopes today, they'll be dangerous where they involve more than about 8  inches of new snow. So this hazard coincides with much of the most attractive terrain for riding today. These conditions will be more widespread at upper elevations, where more snow accumulated over the weekend. 

    Before committing to ascending or descending steep slopes,  assess whether you can escape triggered sluffs and where you might be carried if caught. Confined terrain like chutes and couloirs will make riding out of moving sluffs difficult. Otherwise harmless sluffs can have consequences if they knock you off your feet or machine above a terrain trap, like a gully or dense brush. If you see rollerballs fanning down a slope above you, move to terrain that's not below steep start zones.

    Slope cuts can be an effective tool in these conditions, so long as they're done in a spot that allows you to stay above the hazard and escape any triggered slides. Don't be too low, too slow, with nowhere to go. 

    On isolated slopes, the snow may form small, shallow slabs as it settles.  The terrain management remains the same. 

    (2/3/2023)

    Loose Dry sluff resting on a crust in the Whitefish Range.  Otherwise harmless sluff can have high consequences if you get pushed off your feet into a terrain trap. Photo: Mark Dundas

  • Wind Slabs

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

    In the highest, most exposed terrain, you may find small, soft slabs in spots that collect wind-blown snow - the tops of chutes, the leeward sides of ridges, and steep, convex rolls downwind of saddles. Triggering these slabs can be dangerous on steep slopes above terrain traps. This hazard should be isolated to peaks and ridges above about 7000 feet near the crest of the Swan, Flathead, and Whitefish Ranges. 

    (12/19/2023)

    An example of a small wind slabs that may be found on the leeward side of ridgelines.

    Photo: guy zoellner

Avalanche Discussion

And there was much rejoicing... A few inches of new snow above made for good if noisy riding Sunday.  Riders also reported easily-triggered sluffs that ran far on an underlying crust. Most were harmless because they didn't involve that much snow. I expect this hazard to persist today. The surface snow will likely settle as temperatures warm today, making for denser but slower-moving debris. In a few spots, the fresh snow may form small shallow slabs as it settles. These are unlikely to propagate far, and the risk reduction practices remain the same - avoid steep, confined slopes above terrain traps. 

Riders and remote weather stations reported calm to light winds Sunday, with little to no blowing snow. The exception was Aeneas Ridge, a perenially windy location that's often representative of conditions near ridge crests and summits. In this terrain, you may find some small, dense slabs on steep slopes that collect wind-blown snow - the tops of chutes, downwind of saddles and passes, and crossloaded behind rocks. If you encounter drifts that crack around your feet or machine, step back and assess the consequences of getting caught and carried. 

We've removed Persistent Slabs as a listed hazard. You can still find soft facets around a hard crust on many mid- and upper-elevation slopes. The facets are moist and rounding and we have no reports of whumpfing collapses since the warmup, and few reports of propagation in tests. A supportable surface crust makes it even less likely a person could collapse the facets and propagate a fracture. In steep, high-consequences terrain, it's still worth digging to look for and test this structure before committing.

A report Sunday from near Essex in the Flathead Range did describe a test that propagated on a more recently buried layer on an upper elevation, northeasterly slope. Another report from a similar slope near Pinnacle did not describe this layer. Bottom line: Any whumpfing collapse should stop you in your tracks. Digging to investigate the snowpack is almost always useful. 

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