Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist last year abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The avalanche danger increases with elevation today. The more dry and drifted snow you find, the greater your chances of triggering slabs that can be dangerous where they're more than about 8 inches thick. The best and lowest risk riding today will be on lower-angled, wind-sheltered slopes.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Your excitement may rise as you climb higher in elevation today and find more new, dry snow. The avalanche danger will also be rising with elevation and time, as increasing winds drift more snow. Slabs of new and drifted snow will be reactive to a rider's weight today, breaking in the new snow or on lower-density snow that fell earlier this weak. They can be dangerous where they're more than about 8 inches thick. 

    The best and lowest risk riding today will be on moderately angled slopes that are sheltered from the wind. Think parent pow or hippie wiggles. Boondocking in the trees. While the riding might be deeper in open bowls, those are also the slopes where slabs will be largest and most sensitive to your weight. 

    You can get reliable clues to the size and sensitivity of this hazard with active tests - sidehilling road cuts and other short, inconsequential slopes. Stomping on the uphill side of switchbacks or your uptrack. Dropping chunks of cornice down a slope. Shooting cracks are reliable signs you've found wind-stiffened snow sensitive to your weight. Whumpfing collapes are bulleye info that the dense new snow can collapse and propagate a fracture on drier, low density snow below. 

    (12/28/2024)

    The crown of a skier-triggered soft slab that's typical of today's hazard.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    Lurking 2 to 3 feet below the surface are layers of weak facets and buried surface hoar that formed in January. On isolated slopes, you can still trigger hard slabs that break on these layers. The chances are low, but the consequences would be high. 

    This week's snow is making it harder to identify the slopes where this hazard remains, because crowns and debris from the February avalanche cycles are getting covered. Considering a slope's shape or profile might help now - convex, unsupported slopes are suspect, as are slopes where snow depths tend to be more variable due to scouring and drifting. Those are the same slopes where today's Storm Slab hazard will be greatest, so you're not going to be on those anyway, right?

    I'd avoid spending much time below steep, leeward start zones today. With strong winds today, small natural wind slabs and cornice falls are possible. These large triggers could release thicker hard slabs. 

     

    This recent slab avalanche shows the kind of terrain where the Persistent Slab avalanche problem lurks: steep, unsupported upper elevation slopes. 

    Photo: Michael Reavis

Avalanche Discussion

Wednesday was a four-hard shell day in the Flathead Range, according to Mike. He only brought three and was soaked by lunch. Meanwhile, WMR Patrol reported dry, cohesionless snow and small loose snow avalanches. The variability coupled with more snow and winds today makes for complicated, dangerous conditions up high. 

Areas with the deepest, driest snow will have the most dangerous conditions today. That will be upper elevations, where temperatures were cooler and more snow fell. And there's more snow to blow around, as winds increase today and more snow falls. This hazard may be more isolated in the Swan Range, where snow lines seems to have been highest and forecasts aren't predicting much snow today. We did get a few isolated reports of surface hoar early this week, so it's possible some sheltered slopes may be unusually sensitive to a rider's weight. 

The Persistent Slab problem - the potential for triggering a hard slab that breaks 2 to 3 feet deep - remains. The warm weather the past few weeks has strengthened and consolidated the weak layers of facets and buried surface hoar that developed in January. Recent slides and some propagating column tests indicate that these layers aren't fully dormant, however. It's worth the effort to avoid traveling under steep, leeward upper elevation slopes today, particularly those where you see active loading occurring. The January weak layers may be sensitive to the weight of large triggers, like falling cornics and small wind slabs. 

Curious about recent developments in tele boots and bindings? Check out Telefestivus at Blacktail Ski Area on Saturday, March 22 and Sunday, March 23. In conjunction with the mind-freeing event, Tamarack Brewing will host a fundraiser with a raffle and film for the Friends of the Flathead Avalanche Center from 5 to 8 PM Saturday, March 23. 

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