Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Cooler temperatures are decreasing but not eliminating the hazards associated with this week's unusually warm weather. Triggering a large slab avalanche in the mushy snow beneath this morning's surface crust is possible. Meltwater in the snowpack could cause a glide crack to fail catastrophically.  Move to lower-angle terrain if the surface crust is unsupportable. 

Problemi valanghivi

  • Glide Cracks

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Area SNOTEL stations report modest SWE loss over the past few days, indicating water is moving through the snowpack. Where the water reaches the snow and ground interface, weakening occurs. If a glide crack is present, a large destructive avalanche involving the seasonal snow cover could occur. Today's cooler temperatures and cloud cover will limit the production of meltwater. However, there remains plenty of free water in the pack to keep this problem on our radar for another day. 

    Predicting if and when these unusual avalanches will occur is difficult at best. The best way to mitigate this problem is to avoid traveling beneath slopes harboring glide cracks. Although found on all aspects and elevations, these cracks appear to be concentrated on sunny slopes at mid-elevations.  

    (3/1/2025)

    This glide crack succumbed to the heat of the day Saturday, 3/1. The resulting avalanche was very large (D3).  

    Photo: Flathead Avalanche Center

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–3

    Meltwater from this week's above-average temperatures, rain, and strong sun reached buried weak layers, resulting in large slab avalanches. This morning, you may find a thin surface crust capping a thick layer of moist to wet mushy snow. In locations without a crust, or where it does not support the weight of a rider, triggered slides are possible. 

    Slopes most suspect are those that did not experience the brunt of avalanche activity this week. Generally, upper elevations on the shady side of the compass fared the best; however, wet slabs are unpredictable, and slides could occur on any slope. 

    This week's weather weakened ridgeline cornices, resulting in cornice falls and general sagging in these large features. As these large blocks of wind-blown snow trundle down the slope, they can trigger an avalanche at the surface or deeper in the pack. 

    Continue to choose lower-angle terrain until this weekend's cooler temperatures make travel on steeper slopes more manageable and safer.

    (3/26/2025)

    Multiple soft slab avalanches at a low elevation of Nyack Mountain. These likely failed during a recent high precipitation intensity event that included wet snow transitioning to rain. Some of these crowns are likely wet slabs.  

    Photo: Mark Dundas

Avalanche Discussion

Colder air entered the Flathead overnight, dropping temperatures 10 to 20°F at mid- and upper-elevations from Thursday morning readings. Most mountain stations dropped below freezing around midnight, with Snowslip recording a relatively chilly 21°F as of 0600, 20°F below the temperature recorded yesterday morning. Exceptions are Stahl Peak and Noisy Basin, which remain several degrees above freezing. 

A surface crust has likely formed in many locations exposed to the sky, especially on the windward slopes where W-SW winds provide additional cooling. Today's cool and cloudy conditions will minimize the wet snow problem that has plagued our area over the past few days, allowing us to drop the danger rating in all zones today. However, we have only experienced a few hours of temperatures below freezing, and the snow surface is far from being considered locked up in many areas. The lack of a solid refreeze and today's warming temperatures could allow the crust to break down, allowing for riders to impact the thick layer of wet, mushy snow beneath. Cool conditions through the weekend should allow us to remove wet slab and glide from the problem list. 

The snowpack took a significant hit from this week's weather, with snow depths decreasing by 9-22 inches at mid-elevations. The low-elevation snowpack is melting away, as evidenced by 1.7 inches of SWE lost at the Emery Creek SNOTEL. The Flathead River is cresting this morning at 6,490 cfs, which is more than eight times higher than it was last Sunday. Fortunately, cool, wet weather is expected for the coming week, which should add to our snowpack.

Eastern Oregon University is conducting a survey to better understand avalanche safety preparedness among motorized backcountry users. The survey will help us learn more about who is purchasing and practicing with avalanche rescue gear (beacon, probe, shovel) and participating in avalanche education—and why some riders are not. The survey is confidential and anonymous.Your feedback is invaluable in improving avalanche education and awareness. Please take a moment to share your experience and help us make a difference:

https://eoustmhs.qualtrics.com/jfe/form/SV_3L8QKAuZzcxJBLo

 

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