Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

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

We've observed numerous large and destructive natural avalanches since Tuesday. You are very likely to trigger similar slides today—especially in steep, recently wind-drifted terrain. Avalanches may be triggered remotely—from below, above, and to the sides of steep slopes.

Lawinenprobleme

  • Persistent Slabs

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

    This zone picked up 1-1.5" of SWE since Tuesday afternoon. This load was enough to cause a widespread avalanche cycle in the Sawtooths and the Smoky Mountains. Avalanches occurred on many different aspects, in both obviously wind-loaded and generally sheltered terrain. 

    A weak layer of sugary facets buried in mid-December is responsible for the vast majority of natural and human-triggered avalanches so far this season. If we've learned anything from previous storms, it's that this weak layer doesn't like to be poked and it can remain irritable for days following a storm. A spate of human-triggered avalanches followed each of our last two storms and we should expect human-triggered avalanches to be very likely again today. 

    Remotely triggering slides from below, above, and to the sides of steep slopes is likely. Continue to avoid avalanche terrain, particularly where you find stiff, freshly formed wind slabs near the surface.

    (1/13/2021) This very large avalanche occurred in the Sawtooth Mountains during the intense storm on 1/12-1/13.

  • Wind Slabs

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

    Yesterday's strong to extreme SW-W-NW wind rapidly built fresh wind slabs. Expect to find both hard and soft slabs in many locations. These slabs will be thicker and more widespread at upper elevation, but touchy wind slabs may exist in exposed terrain at any elevation. Cracks shooting from your boards or sled are the best indication that you've found a sensitive slab. Wind slab avalanches that release near ridgelines could "step down", failing on layers deeper in the snowpack and becoming much wider than the initial avalanche. 

    Wednesday's strong to extreme wind built fresh wind slabs on many slopes.

Avalanche Discussion

Tuesday and Wednesday's storm dropped anywhere from 0.5-1.5" of SWE. For storm totals across the forecast area, check here. Although precipitation diminished early in the day yesterday, strong to extreme W and NW wind continued to load slopes at all elevations. As one observer stated, "we were looking up into the Boulders all day watching active wind transport and expecting naturals to release".  I shared the same thoughts as I walked out Titus Ridge near Galena Summit. You can see a short clip of active wind-loading here. 

The uncharacteristically weak nature of the facets in the lower third of the snowpack has produced widespread natural avalanche cycles with relatively light loads. This last storm, while not huge, again tipped the scales. Continued wind-loading for several hours following the storm has only added to the problem. Yesterday, as I looked south along the Smoky Crest nearly every steep slope between Titus Lake and Titus Peak had avalanched. Ben spotted numerous, meaty slab avalanches in the Sawtooths (photo, photo, photo). Large avalanches were also spotted in the Boulders. This of course is only a partial list. We didn't get a good look at the Soldiers, or mountains near Banner Summit but given the track record of this weak layer, it's not going out on a limb to expect to see evidence of natural activity there as well. 

The lure of fresh snow and mild weather over the next few days will be strong. Trust me, I get that, but I urge you to build an extra safety margin into your travel plans. The weak layer we're dealing with is special, but I hesitate to call it "unpredictable". We've seen what it can do, and we know it can be touchy for days after a loading event. Don't lose sight of those facts as you choose where to ride this weekend.  

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