Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering a large avalanche remains a possibility—primarily in wind-affected terrain. In these areas, a slab may exist atop a buried weak layer. To reduce your risk, avoid slopes with evidence of wind, such as fresh drifts or a stiffer snow surface that supports your sled or skis.

A strong storm will impact the area beginning Sunday, creating dangerous avalanche conditions. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2.5

    It is still possible to trigger a slab that breaks 1 to 2 feet deep on thin layers of weak snow above the very hard, early February ice and crust layer. These layers are better developed on shady, upper-elevation slopes but are also found on isolated sunny and mid-elevation slopes. 

    Recent mild temperatures are helping to strengthen the weak layer, but this process is notoriously slow. You may not experience any signs of instability like collapsing or cracking before triggering a slide. 

    Choose terrain free of convexities to increase your safety margin. Steer around thin areas, such as those scoured or peppered with rocks, in favor of a deeper, more consistent snowpack. Cracking beneath your boards or machine indicates an unstable slab directing you to lower-angle terrain. 

  • Wind Slabs

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

    West and southwesterly winds developed Friday, increased overnight, and will remain elevated today (Saturday). In most windward locations, only several inches of snow are available for transport, which will limit drifting. However, expect to find thin, fresh slabs reactive to the weight of a rider downwind of ridgelines, saddles, and on sidewalls of cross-loaded gullies. These slabs will increase in size and thickness as you gain elevation.

    Drifts, dunes, and rippled snow surfaces confirm that the wind has been working. Blowing snow and cornices point in the direction of slab formation. Cracking beneath your machine or boards indicates instability, directing you to safer, sheltered terrain. 

    Wind slabs will form on the same slopes that harbor our persistent slab problem. Triggering a small wind-drifted feature may initiate a much larger avalanche. 

     

     

    (2/23/2024) The prevailing wind blows from right to left in this image. The small cornice line is evidence of wind drifting with potential slab formation beneath the ridgeline.  Photo: David Kerner

Avalanche Discussion

A robust Pacific storm system will move into the area on Sunday, with heavy snow and blustery winds creating dangerous avalanche conditions. If the forecast verifies, we may reach CONSIDERABLE danger on Sunday and perhaps HIGH on Monday. Unsettled weather continues throughout the work week, keeping the hazard elevated and new snow avalanche problems on the list. 

Today (Saturday), we will primarily experience the effects of wind, with the chance of light snow showers developing this afternoon. Due to moderate sustained west and southwest winds, we added wind slab to the problem list. Overnight wind speeds were impressive, with gale force gusts (greater than 38 mph) at many upper elevation stations, with 88 mph recorded at Tunnel Ridge. Despite the limited snow available for transport, riders noted wind-drifted snow filling in their skin track along with small reactive cornices in southern Glacier Park.

The last recorded avalanche on a buried weak layer occurred on Monday, 5 days ago. This week's relatively mild temperatures are helping to strengthen this layer found 1 to 2 feet below the surface. Today's wind loading will initially test this weak snow, but the heart punch begins tomorrow with the heavy snow and drifting.  

In the southern Whitefish Range, three groups from the Patrol Fund Level 2 avalanche course submitted observations from just east and west of the ski area (Observation 1, Observation 2, Observation 3). Numerous snowpit tests resulted in non-propagating results except for an ECTP 28 down 37 cm on a south aspect. They looked but could not locate the buried surface hoar (photo) that Rob noted Thursday. 

Friends Fest is Here! Today, February 24th, is the last day—Hot Dog Days at the Canyon Creek trailhead and the top of Flower Point chair at WMR. Don't miss the Ultimate Après with Backcountry Partner Speed Dating and the Big A$$ Raffle. More info at flatheadavalanche.org/event/friendsfest

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