Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

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

The avalanche danger will rise to MODERATE as snow and wind build sensitive drifts. These drifts will be thicker and more widespread at upper elevations that are exposed to the wind. Dry snow avalanches are possible in very steep, sheltered terrain. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Storm totals in the Banner Summit Zone should reach 4-8" by nightfall. Wind has blown light (so far) but a cold front will pass through this afternoon kicking-up wind speeds from the NW followed by moderate NE wind after the front moves through. 

    Expect small wind slabs to grow in size and distribution throughout the day. These slabs may be touchy, particularly where they rest on facets and crusts that formed over the past few days. Spring storms have the tendency to produce heavy, localized precipitation and gusty wind. These heavier bursts of snow are more likely this afternoon. 

    Look for pillowed or drifted areas on the lee sides of ridges (photo above/right), gullies, and other terrain features. 

    This small wind slab released on a wind-loaded upper elevation ridge in the Boulder Mountains near Senate Pk. SW-aspect near 10,100'. Photo: J. Preuss

Avalanche Discussion

Spring Storms

Ah yes, spring storms. One minute you're buffeted by strong wind and blowing snow and the next you're stripping layers and pulling out the sunscreen. Last night, the leading edge of such a storm arrived near Banner Summit and will slowly move across the forecast area today, eventually departing in the early morning hours tomorrow. 

The impacts of spring storms can be highly localized. Snow totals can easily double (or half) from one drainage to the next. Wind can be erratic, blowing from a variety of directions, or in some cases can be eerily calm. This variability is produced by the enhanced convective nature of spring storms; think deep, towering cumulus clouds rather than thin, low stratus. Localized up-drafts enhance snowfall rates and are often coupled with moderate to strong wind. 

So if the weather is the architect of the snowpack, what's in the plan for today? 

  • Wind Slabs: The equation for this problem is simple, snow + wind = wind slab. However, the size and distribution of this problem will likely be sporadic, for the reasons discussed above. I think the best way to deal with this hazard is to expect to find it at upper elevations and be pleasantly surprised if you don't. Unfortunately, today's slabs will mask evidence of those that formed during the NW-N-NE wind on Tuesday (photo). Yesterday, a skier triggered one of these small slabs in alpine terrain of the Smoky Mountains. 
  • Dry Loose: As snow accumulates, your odds of triggering loose snow avalanches or "sluffs" will increase. You're most likely to find this minor hazard on slopes greater than about 40 degrees. 

Wind slabs and dry loose avalanches are more likely later this afternoon, particularly as wind speeds and snowfall rates increase. Today, flexibility is the key to success. Give yourself some options. Be prepared to turn back, or pick simpler terrain as mountain travel becomes more challenging throughout the day. 

Regions covered