Lawinenlagebericht

Swan Range

Flathead Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Dangerous avalanche conditions are developing.  Wet, dense snow and blowing snow is overloading the previously dry, soft surface snow. You could likely trigger an avalanche in freshly formed slabs. We recommend sticking to sheltered lower angle slopes without steep slopes above for a safer experience.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    2–3

    Overnight, intense precipitation rates, gusty winds, and rising temperatures deposited a dense layer of snow on top of our previous low-density surface. These upside-down near-surface conditions began developing Saturday afternoon, with observers noting cracking and thin slab avalanches. Conditions worsened overnight, and we assume a natural avalanche cycle occurred. Today's slabs will be identified by cracking underneath you or your machine, dense, stiff surface snow that keeps you from sinking more than a few inches into the surface, and possibly hollow-sounding snow. If you venture out today, choose low-angle terrain free of overhead hazards.

    (12/18/2021)

    Thin storm slab avalanche triggered by a tree bomb east of WMR.

    Photo: Lance Young

Avalanche Discussion

Saturday, moisture-laden pacific air entered our area mid-day with light snow and rising temperatures. Observers reported surface cracking and thin, small avalanches becoming more common throughout the day (Example 1 Example 2, Example 3 ). The storm ramped up overnight with intense precipitation rates, moderate to strong winds, and rising temperatures. Favored locations include the northern Whitefish Range, where the Stahl Peak SNOTEL reported 1.9 inches of water with 1.6 inches in central Glacier Park at the Flattop SNOTEL. The usually reliable Noisy Basin SNOTEL in the Swan Range received a mere 0.7 inches of liquid. Due to dense snow falling onto and compressing a soft snow surface, new snow totals are difficult to interpret at remote weather stations. Manual snow study plots provide a more accurate observation in these conditions, with the WMR station reporting 9 inches of new snow in the past 24 hours.

This is the first AVALANCHE WARNING we have issued this season. We don't publish these lightly but are concerned that the dense new snow is overloading the previous low-density surface snow. Those that have gotten out recently have enjoyed excellent riding conditions of deep powder resting on a strong basal snowpack. Observations from all zones mentioned a right-side-up snowpack. Unfortunately, conditions have dramatically changed overnight, and we suggest avoiding riding in or beneath all avalanche terrain today in the Flathead Range, the Whitefish Range, and Glacier Park. We have not included the Swan Range in the AVALANCHE WARNING  due to less precipitation that has fallen there. However, we still anticipate dangerous avalanche conditions in the Swan and recommend you dial your terrain choices back to a conservative level.

Check out the new Conditions Blog tab for a great summary of conditions leading up to the big storm.

Abgedeckte Regionen