Lawinenlagebericht

Swan Range

Flathead Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Continued winds and snowfall increase your chance of triggering an avalanche in wind-drifted snow. Look for and steer around deeper pockets of snow near ridgelines, beneath saddles, and in gullies. Terrain sheltered from the wind offers a safer experience.

The avalanche danger will rise overnight into Monday as a powerful storm impacts our area.

Lawinenprobleme

  • Wind Slabs

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

    Gusty southwest winds continue transporting Saturday's snowfall. Light snowfall today will fuel the fire forming fresh slabs of wind-drifted snow and thickening recent slabs. Slabs reactive to the weight of a rider will be larger and more dangerous on the downwind sides of ridgelines, beneath saddles, on the sidewalls of gullies, and around prominent terrain features. 

    Look for blowing snow as you gain elevation to identify locations of wind-drifted features. A rippled surface and dune-shaped mounds indicate that the wind has been at work. Cracking beneath your feet or machine is a sign of instability. A shooting crack is a red flag directing you to sheltered terrain or a lower-angle slope.

    Loose Dry: The surface snow remains loose in most areas sheltered from the wind. Anticipate triggering a Loose Dry sluff on slopes steeper than 35 degrees. Fresh snow is resting on various surfaces, including crusts which may inhibit bonding. Manage your sluff and limit time spent above terrain traps or in long-running gullies.

     

    (2/16/2023)

    Recent snowfall was readily blown around at upper elevations from southwest winds.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–3

    A weak layer of snow exists 2-4 feet beneath the surface in the Swan Range. Triggering this layer is becoming more difficult but remains possible. A slide in today's fresh snow has the potential to step down to a buried weak layer. The suspect layers are found on all aspects but are most developed and troublesome on shady aspects at mid and upper elevations.

    Dealing with a Persistent Slab problem is tricky. The only way to identify that a slope harbors this problem is to dig down to see if this weak layer exists. The easiest way to manage this issue is through terrain selection. Choose lower-angle planar slopes free of convexities. Steer around areas harboring a thin snowpack, such as wind-scoured or having a rocky peppered appearance, where the weak layer is closer to the surface and more susceptible to the weight of you or your machine. 

    (2/15/2023)

    the new 2/10 crust.

    Photo: Guy

Avalanche Discussion

As I mentioned yesterday, we have had nearly seven weeks of relatively bland and benign avalanche conditions. With deep powder in the forecast, we must approach the next few days with our avalanche eyeballs wide open.  Look for signs of instability in your travels and ease into larger terrain. 

Yesterday's storm met expected snow and water amounts in the Whitefish Range, where around 6 inches of snow and up to 0.7" of SWE were recorded. However, totals in the Swan Range and the Flathead Range were only about half of what was forecast. Noisy Basin picked up 1.0" of SWE with the Flathead Range receiving around 6" of snow and southern Glacier Park recording slightly less.

Today, we have downgraded the danger rating at all elevations in the Flathead Range due to yesterday's underperforming storm. We have also downgraded the Swan Range at the low and mid-elevations to reflect the same. The Whitefish Range remains steady.

Due to yesterday's modest snow totals, we have dropped the storm slab from today's problem list. However, today's snowfall combined with slightly warming temperatures may form isolated surface slabs in sheltered terrain. These features have similarities with wind slabs and can be identified by slightly denser snow that may crack underneath you. Choose a different slope or lower-angle terrain if you encounter this problem. 

Light to moderate snow is expected to develop today. If the snowfall exceeds anticipated amounts, the danger may rise and be slightly higher than forecast.  Precipitation intensifies overnight and into Monday. This wave will be followed by a well-advertised Atmospheric River that will impact the area. Storm totals of up to 3.0" SWE have been downgraded, but we should still receive a welcome dose of moisture. Northeast winds and arctic air arrive Tuesday and last through the work week.

Expect the avalanche danger to rise overnight and remain elevated through Tuesday. If the forecast verifies, we may reach HIGH danger in parts of our area.

Weather trivia: 

  • Friday, Missoula recorded the 100th straight day of snow on the ground. This is only the fifth time Missoula has reached this milestone and the earliest date ever. The record is 122 days set during the 1996-97 season. 
  • Kalispell has recorded 89 consecutive days with snow on the ground at KGPI. This streak spans from Nov 23, 2022, to Feb 19, 2023. That makes this the 31st longest streak.

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