Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Recent winds continue to form and build slabs and drifts in alpine and upper elevation terrain. Be cautious on steep slopes where you find wind-drifted or pillowed snow. Slopes where you could trigger weak layers buried 2-4 feet deep are becoming few and far between, but it may remain possible on very steep, rocky, wind-affected slopes at upper elevations. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    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

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Erratic, gusty winds yesterday and last night transported snow in exposed terrain. On some slopes, the wind likley formed thin new slabs or built existing wind slabs. Yesterday, SAC staff observed some isolated cracking—but no avalanching—on steep middle and upper elevation slopes in the Banner Summit area.

    This problem will be most common in alpine terrain and at upper elevations where it remains possible to trigger slides on slopes over about 35 degrees in steepness. The slabs could be more sensitive to triggering where they overlie hard, wind-polished surfaces or crusts.

    Watch for smooth pillows of stiff or hard snow, dunes, or wave-like patterns on the surface. If you see cracks shooting out from your skis or sled, consider where even a small avalanche could carry you before riding that really steep slope. 

Avalanche Discussion

LOW does not neccessarily mean NO: Today is the first day of the year with LOW danger at all elevations in any of our zones (Wood River Valley & Soldiers). What is LOW avalanche danger? Most slopes are safe, but not all slopes are safe. If you dropped 50 people off and told them to ski or ride the steepest, middle and lower elevation, wind-loaded slopes they could find in this zone, 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.

Today's canvas is tomorrow's problem: The recent spell of cool, sunny weather has created weak surface snow on some aspects and elevations. In mid-February in south central Idaho, the combination of the sun angle and cool, winter temperatures can produce excellent conditions for a process called near-surface faceting. At the snow surface, you'll notice a variety of crusts and "recycled powder" (facets) that sound and feel "hissy" when you're skiing or riding. If we get a decent shot of snow this weekend, we may see avalanche activity on relatively thin slices of the compass where the weak layer is "just right". Noting the variety of the snow surface today can help you wrap your head around how dramatically stability may change with minor changes in aspect or slope angle this weekend. 

Regions covered