Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
3 · Erheblich
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Kernpunkte

A warm, potent storm is creating very dangerous avalanche conditions. Expect large natural avalanches that run long distances. Stay off of and out from under steep slopes. 

The danger will rise throughout the day and overnight as temperatures continue to warm, winds strengthen, and precipitation intensifies. 

Lawinenprobleme

  • Storm Slabs

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

    Ongoing heavy, wet snow forms dense slabs on softer, drier snow in all aspects. These upside-down near-surface conditions will decrease the stability of the new snow. They will be most dangerous where wind-blown snow forms a thicker and stiffer slab. 

    Natural storm slab avalanches large enough to bury people are expected. These will become more reactive and larger throughout the day and overnight as rain, snow, wind, and warm temperatures continue.

    Avalanches in the new snow have the potential to initiate a larger, more dangerous slide on buried weak layers described in our Persistent Slab problem. Avoid steep slopes, overhead hazards, and the runouts of avalanche paths.

    (4/7/2024)

    This avalanche failed in the storm snow and is a soft slab avalanche. This is the type of slide that could occur with a storm slab problem.

    Photo: Jeff Metsky

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–2.5

    Precipitation and wind overnight and today will likely initiate a natural avalanche cycle on weak layers buried 1-3 feet deep. Sugary facets, surface hoar, and faceted crusts may reach their breaking point, resulting in large avalanches with long-running debris. 

    Conditions are most dangerous where wind-blown snow forms thick, stiff slabs; however, avalanches are also likely to occur in sheltered terrain. 

    Persistent Slabs can release in surprising ways and break wider than expected. Avoid avalanche terrain, including connected lower-angle slopes.

     

    (2/13/2025)

    A large natural avalanche triggered by a natural cornice fall from the ridge above. The intial debris stepped down to older weak layers as it ran down slope. SS-NC-D2.5R2-O

    Photo: Flathead Avalanche Center

  • Loose Wet

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

    Below the snow line, heavy rain is saturating and weakening the surface snow. Natural wet loose avalanches are anticipated throughout the day on steep slopes receiving rain. Loose slides may also occur in today’s moist snowfall. Wet slab avalanches may develop later today as moisture penetrates the snow surface. 

    Surface slides could trigger a larger slide on buried weak layers described in our Persistent Slab problem.

    Snow peeling off rock faces or dropping from trees can initiate a natural slide. Rollerballs are a precursor to a wet loose slide. Stick to lower-angle slopes free of terrain traps and overhead hazards. Call it a day if you are sinking in sloppy, manky snow. 

    (3/17/2024)

    This is a view of about a dozen wet loose slides originating on south-facing mid-elevation slopes. Heavy rain and rising freezing levels will likely produce slides like these during the current Atmospheric River event.

    Photo: Mark Dundas

Avalanche Discussion

Overnight, moisture from an Atmospheric River entered the Flathead, which was accompanied by mild temperatures, a freezing level of around 5000 feet, and blustery winds. As of 0500, up to 0.9 inches of water has been recorded at area SNOTELs. Oddly, Noisy Basin has not recorded any SWE, but they are favored for 0.8 inches through the day. Precipitation continues into the afternoon with increasing freezing levels and elevated winds. Another wave of moisture and wind will affect our area tonight before this system runs out of gas early Monday morning.  

Over the past five weeks, the Flathead has enjoyed a lengthy period of cold weather (Graph). This has preserved low-density surface snow in sheltered areas and limited the strengthening of the widespread buried weak layers. We anticipate a natural avalanche cycle but are unsure to what degree this quick-hitting storm affects our buried weak layers.

Today is the first day of the 2024-25 season that the avalanche danger is rated at HIGH. This season's lack of days with elevated danger is unusual (Graph). Today would be a good day to skip recreating in the backcountry. If you must head out, stick to well-beaten roads and trails far from avalanche terrain, including overhead hazards. This will limit the wallowing you will inevitably deal with in areas with a saturated snowpack and keep you safe from avalanches. 

Upcoming Events: Check out our calendar and sign up now!

  • Feb 26th - State of our Snowpack Presentation at 7 pm for Pint Night at Blackstar with donations going to Flathead Avalanche! 

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