Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
View on map

Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
Open full map
Out of date — this forecast expired 7 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

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. 

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

    A stiff west wind and light snowfall this morning may combine to form fresh, sensitive wind slabs. These thin slabs will build upon older, stiffer slabs that formed during Tuesday afternoon's gusty NW-NE wind. Wednesday 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.

Looking Ahead: A passing cold front this morning will kick off a blustery, cold, and snowy weekend. Snowfall amounts in the next couple of days will be light, but it can be surprising how quickly fresh slabs can form with a persistent wind. Snowfall will increase Saturday night and weather models predict around a foot of new snow in some portions of the Banner Summit and Sawtooth & Western Smoky Zones by Sunday afternoon.

Our field objectives over the last couple of days included checking in on the snow surface to get a better sense of what this snow will rest on. You can read Chris and Martins' thoughts from yesterday near Williams Peak in the Sawtooth Mountains here. They concluded, "I could see some potential instability with the weekend storm but it doesn't seem likely that it will be extensive or long-lived in this area. "

Wednesday, in the Soldier Mountains, the conditions were very different. I found an ugly and relatively widespread crust and facet combination at middle elevations (video). Warm temperatures at the end of January and early February built a stout crust. Since then–unlike the snowier regions to the north–the Soldiers received very little snow. In sheltered areas, this tiny amount of snow was allowed to facet and surface hoar sprang up on shaded slopes. 

I highlighted these two examples to help point out the spatial variability we might expect with this weekend's storm. By late winter and spring, temperatures near or above freezing, heavier and more localized precipitation events, and strong solar radiation can produce a wide range of conditions over a short distance, not to mention zone-to-zone. As you head out to enjoy the snow, keep this variability in mind and frequently check-in to see how the new snow is bonding with the old snow surface. 

Regions covered