Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Pay attention to new snow problems in the Flathead and Swan Range today, where more snow fell recently. Look for and steer around wind-drifted snow and dial back your terrain choices if you see shooting cracks or recent avalanches. Wind slabs will become larger in size the higher you climb. In wind-protected terrain, manage loose dry sluffing with defensive riding strategies.

Lawinenprobleme

  • Wind Slabs

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

    Anywhere from four inches to possibly a foot of snow was blown into stiff slabs Sunday night. Observers reported wind loading on a southeast aspect high in the Flathead Range yesterday (Monday). I suspect wind slabs are gaining strength; however, slabs of drifted snow now rest on weak faceted snow, crusts, or stiff wind board. I recommend objectives sheltered from the wind and giving freshly formed slabs time to adjust. Terrain sheltered from the wind will also be where the higher-quality riding is.

    (1/9/2023)

    Guy doing a hand hardness on the upper part of the snowpack. We found a thin slab (shown in the cut out block) and a layer of near surface facets above the Christmas crust. 

  • Persistent Slabs

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

    We are currently in a holding pattern since the last audible collapse on January 6th. This collapse appeared to be loud and significant enough to shift the snowpack. We remain wary of removing the problem due to the consequences at stake. Our primary advice for you all chasing steeper objectives is to select slopes with less consequential runouts to reduce the chances of trauma or deep burial.

    (1/7/2023)

    A very large avalanche which failed during the rain event sometime between December 26 to December 28. 

    Photo: Kevin Oberholser

Avalanche Discussion

A ridge of high pressure settles into the forecast region today. Winds shifted to the north yesterday (Monday) afternoon. This wind shift dropped wind speeds to single digits and brought cooler air. Temperatures will climb back up 30 degrees F at roughly 6000 feet today. Cloud cover appears to drift back and forth between clear and partly cloudy.

This weather pattern will do little to change the avalanche danger. The primary change we may see today is if the sun sticks its head out longer than expected. This may cause a few loose dry sluffs out of steep, rocky terrain in the new snow. If this happens, I suspect they will be primarily small and easy to manage. One "defensive riding strategy" for managing sluff is to cut across the top of the slope and allow your sluff to run before descending. One observation from yesterday noted southerly aspects getting cooked in the Flathead Range while the southern Whitefish Range remained in the clouds. There is a lower likelihood for this to happen in areas with a sun crust from yesterday.

Many of the recent observations note variable wind-drifting. Some recent drifts have altered riders' planned objectives and directed them to wind-sheltered slopes. I will take this and run with it today. First of all, there is less of a chance of triggering a slab avalanche that is potentially large enough to bury you in wind-protected terrain. Secondly, the riding quality is better where winds haven't drifted or scoured the snow surface.

We lack observations from the Swan Range, where more snow fell Sunday night. This snow has fallen onto various weak surfaces and may behave more like a persistent slab problem. If you observe signs of shooting cracks, recent avalanches or can remotely trigger avalanches, take a big step back and select slopes with low angles.

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