Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 7 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering an avalanche on weak layers buried 2-4 feet deep remains a possibility on very steep, rocky, wind-affected slopes at upper elevations. Smaller avalanches are also possible in areas of recently wind-drifted or pillowed snow. 

Lawinenprobleme

  • Persistent Slabs

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

    Early-season persistent weak layers in the lower snowpack are widespread throughout the Galena Summit & Eastern Mtns zone. What's less consistent is the nature and stability of these layers. 

    The thin, windswept snowpack on west aspects in the Boulder Mountains did not respond well to last week's wind events, and several large, natural persistent slab avalanches occurred as a result (see observation and photos below). In the White Clouds, a very large slab avalanche released about a week ago on faceted snow at the base of the snowpack (photo to right). It broke over 500 feet wide, 4-6 feet deep, and covered snowmobile tracks from the previous day. Meanwhile, these same weak layers in the Galena Summit and Baker Creek area are showing better stability. Recent wind-loading could be stressing the weak snow near the ground just enough to keep these large avalanches on my mind.

    While triggering a persistent slab avalanche is generally unlikely, it remains possible in terrain with the following characteristics:

    • Steep: slopes in prime-time avalanche terrain around 35-45 degrees.
    • Wind-affected: heavily wind-loaded by past or recent wind events.
    • Alpine flavor: complex, windswept terrain with rock ribs, cliff bands, or convexities.

  • Wind Slabs

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

    Strong, gusty NW-NE wind Tuesday afternoon and evening likely built thin wind slabs in exposed terrain. Yesterday in the Smoky Mountains, Martin found several generations of stiff wind slab. For the most part, these slabs were unreactive, but he did observe clean shears in one of his snowpack tests.

    Recently formed drifts may still be sensitive where they overlie hard, wind-polished surfaces or crusts. You're most likely to encounter these slabs at upper elevations. Watch for smooth pillows of stiff or hard snow, dunes, or wave-like patterns on the surface. Cracks shooting out from your skis or sled are a sure sign that you've found a sensitive slab.

Avalanche Discussion

LOW Danger: The Banner Summit and Wood River Valley & Soldier Zones are at LOW danger. When the danger is LOW triggering an avalanche is unlikely and most slopes are safe. Could you trigger an avalanche at LOW danger? Certainly, but you'd have to find one of the very few spots in the range with unstable snow. If you dropped 50 people off and told them to ski or ride the steepest, wind-loaded slopes they could find, someone would probably trigger a slab avalanche. It's nearly impossible to definitively predict which slope(s) are "triggerable", but we can hedge our bets by thinking about the consequences of small avalanches where we're playing. If you don't like the looks of what's below you—trees, cliffs, roads or other terrain traps—then move to a different part of the slope or another area altogether.

Today's Canvas is Tomorrow's Problem: As you head out today keep an eye on the current snow surface. Yesterday in the Soldier Mountains, I found an ugly and relatively widespread combination of crusts and facets at middle elevations (video). In relatively sheltered areas, you may notice a variety of thin crusts and "recycled powder" (facets) that sound and feel "hissy" when you're skiing or riding. This is a result of near-surface faceting caused by the combination of the sun angle and cool, winter temperatures. It's looking like we'll have some snow to celebrate this weekend. Noting the snow surface today can help you anticipate how the stability may change with minor changes in aspect or slope angle this weekend. 

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