Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

8 to 14 inches of snow accumulated in the last 24 hours, creating dangerous avalanche conditions. Slabs will be thicker and more dangerous on the leeward side of ridges and gullies. A northeasterly wind event will complicate travel by blowing snow onto usually sheltered aspects. Avoid the hazard by sticking to slopes 30 degrees or less and staying out from underneath large avalanche paths.

Lawinenprobleme

  • Wind Slabs

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

    Moderate to strong southwesterly winds blew new snow into thick slabs on the leeward side of ridges and gullies. Avoid these areas and be cautious in wind-protected areas where new snow rests over weak faceted snow or surface hoar. Slabs may propagate wide distances or may be triggered remotely. On Monday, observations throughout the forecast area noted reactive slabs on a variety of aspects along with audible collapses (observation, observation). Today, winds will shift to the northeast and transport snow onto unusual aspects. Plan your travel to not expose yourself to slopes steeper than 30 degrees.

    (1/31/2022)

    A ski cut triggered this soft slab on a convex roll at 5250 ft in John Stevens Canyon. 

    Photo: blase reardon

  • Deep Persistent Slabs

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

    Weak snow near the ground failed in a handful of large avalanches initiated by a wet, warm storm on January 12. Benign weather, no recent avalanches, and snowpit tests show that this layer is gaining strength and is unlikely to propagate. Recent snowfall will not likely deliver enough load to re-activate this hazard. This problem exists in start zones above 8000 feet and is a low-probability, high-consequence scenario.

    (1/17/2022)

    Crown line of a deep persistent slab avalanche. Crowns estimated at 6 to 8 feet thick. Failed on January 12th. 

    Photo: Mark Dundas

Avalanche Discussion

The best advice I can offer is to make simple travel plans. New snow, shifting winds, and wind chill values of -40 tonight all contribute to a potentially complicated day. Keep slope angles low and avoid wind-loaded aspects all together. New snow and wind transported snow is falling on weak faceted snow, surface hoar, windboard, or a slick melt-freeze crust. On Monday, a rider in the southern Whitefish Range found cracking and slabs releasing in areas protected from the wind (observation). These likely failed on a weak layer of surface hoar or facets. Slabs releasing on these weak layers can propagate wide distances, be remotely triggered, or may not trigger until you are in the middle of the slope. Shooting cracks and whumpfing collapses are signs you found this problem.

Though the storm was a bit late to the party, it still packed a punch throughout most of the forecast area. Tunnel Ridge in the Flathead Range saw roughly 14 inches, Whitefish Mountain Patrol reported 11 inches at their mid-mountain station, and Stahl in the northern Whitefish Range shows roughly 8 inches of new snow. Coming in last was the Swan Range where only 3 inches of new snow is being reported at the Noisy Basin station.

This healthy shot of snow was accompanied by wind speeds averaging in the upper teens and low twenties with gusts reaching 50 mph out of the southwest. This transported snow into slabs one to three feet thick on the leeward side of exposed ridgelines. A curveball will get thrown this afternoon with increasing winds out of the north and east. Wind speeds are expected to gust to 50 mph, drifting snow onto slopes that face west and south. Travel cautiously and bring extra layers today.

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