Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
View on map

Avalanche danger

Thu
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
Open full map
Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Sizable avalanches are unlikely, and most slopes are safe. Watch for isolated wind drifts and cornices at upper elevations. Very steep slopes that directly face the sun could produce small, natural loose snow avalanches (sluffs). 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Last weekend's wind and snowfall formed isolated small drifts and slabs at upper elevations. On Monday near Galena Summit, a skier intentionally triggered a small, recently formed wind slab. In this zone, similar drifts could remain sensitive to triggering where they formed above crusts associated with small faceted crystals.  Check out these videos (Sunday, Monday) to see what conditions were like in the Sawtooth Mtns just south of the Banner zone.

    Watch for smooth pillows of stiffer snow, dunes, or wave-like patterns on the surface. If the new snow depth rapidly increases and feels stiffer than loose powder, you've found a wind slab. Snowpack cracking is an obvious sign that you've found a sensitive drift. These slabs are unlikely to produce an avalanche large enough to bury a person, but triggering one in the wrong place could bring serious consequences.

    Cornices grew in the past couple weeks (see photo below), forming curls and overhangs in some exposed terrain. Give any large features a wide berth.

    ADDITIONAL DISCUSSIONOn slopes that directly face the sun, small, natural loose snow slides (sluffs) are possible today. This scenario will begin on E-SE aspects in the morning, shift to S-facing slopes during the day, and move over to SW-W aspects in the afternoon. If you're seeing small balls of snow rolling downslope, or if the snow surface is starting to feel moist and sticky, pay attention to what's above you. Sun-induced sluffs are most likely in very steep, rocky terrain sheltered from the wind. 

Avalanche Discussion

50 Shades of Green: Not All LOW’s are Created Equal

 You probably noticed today is the first day this season we assigned LOW danger to the entire forecast area.

  • Does that mean most slopes are stable? Yes.
  • Does that mean all slopes are bomber and incapable of producing avalanches? Heck no.

Here’s a quick rundown of specific areas we are seeing different shades of green, or LOW danger:

The White Cloud Mtns: This mountain range almost singlehandedly kept the Galena Summit & Eastern Mtns zone at MODERATE danger for another day or two. It hasn’t snowed much this month, but the snowpack structure at upper elevations remains ugly: a 3-4’ thick, hard slab perched above well-developed depth hoar crystals near the ground (see video).  During a SAC forecaster conference call last night, we unanimously agreed this is the one area we’re not yet interested in skiing or riding steep, rocky, upper elevation terrain. If we were hunting for the rogue avalanche large enough to bury people, this is where we’d go.

The central and southern Boulder Mtns and Pioneer Mtns: Danger-wise, these areas are the White Clouds’ little sibling. The snowpack structure is poor, but the combination of a lack of snowfall and extreme wind events has produced an abnormally thin snowpack. Also, it hasn’t snowed much at all this month. Triggering a large slab avalanche is unlikely, but it is not impossible. The odds of triggering a big slide generally decreases as you move from north to south. 

The eastern Smoky and northern Boulder Mtns (Galena Peak area): Below average snowfall all year has created a fairly weak snowpack that is now generally stable because it hasn’t snowed much in the past two weeks.

The Sawooth Mtns, western Smoky Mtns, and Banner Summit zone:  As usual, these areas have the deepest snowpack in our forecast area. The big January storm (30-50” of snow in 5 days) overloaded the depth hoar and facets near the ground, producing a widespread, deep slab avalanche cycle. Since that storm, this area has received well below average snowfall. The weak layers responsible for the January avalanche cycle look a lot better than they did in January; for now, they are hibernating, or dormant. Also, the weak layers are buried far enough below the surface (typically well over 3 feet) to significantly reduce the chances of people triggering large avalanches.   

The Wood River Valley Mtns south of Ketchum and the Soldier Mtns: This area has received less than 10” of snow this month, and the increasingly powerful sun angle is quickly decimating the snowpack on sunny aspects. Triggering a large avalanche in this area is very unlikely.   

The combination of sunny, spring-like weather and LOW avalanche danger means there’s a lot of fun to be had in the mountains. However, I’d encourage you to always consider the consequences of triggering even a small avalanche before pinning the throttle for that epic highmark or dropping into a committing line off a big peak. Where would the snow carry you if it released? If something “just doesn’t feel right,” there’s probably an underlying reason for your hesitation. While the alpine environment is beckoning, remember that triggering small avalanches is always possible in “extreme” terrain.  

Regions covered