Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Thu
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

The snowfall has stopped, but it is still downright scary out there. Skiers and riders are very likely to trigger avalanches large enough to destroy trucks. Natural avalanches are possible. Avoid all avalanche terrain. Stay off of and out from below steep slopes—slopes steeper than about 30 degrees. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3.5

    Several flavors of large destructive avalanches are possible today. The travel advice is simple: stay out of the way. Read the Forecast Discussion below for details on specific avalanche problems other than the Persistent Slab and Wind Slab problems described in detail.

    What is it? Triggering powerful, 2-5 foot thick avalanches is very likely. Recent snowfall, wind-blown snow, and rain overloaded the buried weak layers (sugary facets or crust + facet combinations) that produced hundreds of avalanches and tragically resulted in an avalanche fatality in recent days. In areas exposed to the wind, slides could release naturally—on their own. Avalanches could be over 1000' wide and may run to the valley floors. 

    Where is it?  Given that we've received snowfall all but one day since February 26th and 1.5-3 feet in a couple of days, the slabs exist on almost all slopes. Wind-loaded slopes are the most dangerous. Many of the slopes that avalanched last weekend have "reloaded" with fresh, dense slabs. Limited observations indicate the weak layers are widespread in the southern part of this zone and appear to be less prominent in the northern Sawtooths.

    How can you recognize it? Avalanche terrain includes slopes steeper than about 30 degrees and areas below steep slopes. Wind-loaded slopes have stiffer, denser snow that keeps your skis or sled from sinking deep into the snowpack. 

    How can you manage it? Stay off of and out from beneath slopes steeper than 30 degrees. Persistent weak layers can fail unpredictably and break significantly wider, deeper, and higher on slopes than you might expect, producing much larger avalanches. Smaller wind slab, loose snow, and storm slab avalanches can trigger larger persistent slab avalanches lower on slopes. You could remotely trigger avalanches from gentle terrain far above, below, or to the sides of steep slopes. Avalanches could be triggered by the second, third, or fourth rider on a slope that initially appears to be stable. 

    (3/11/2023) This very large persistent slab avalanche was observed in the Boulder Mountains. It failed over 3,000' wide, wrapping around S-SE-E-NE aspects between 10,000' and 10,800'.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    Natural and human-triggered avalanches are very likely in wind-loaded terrain. Strong winds formed and will continue to build wind slabs in exposed terrain. Expect to find smooth pillows of windblown snow near ridgelines, beneath cornices, and lower in cirques below large cliff bands and on the aprons of chutes and couloirs. Cracks shooting out in front of your skis or sled are a sure sign you've found a wind slab. 

Avalanche Discussion

We could face 7 different avalanche problems today: persistent slabs, wind slabs, storm slabs, deep persistent slabs, dry loose, wet loose, and cornice. How do you manage something that complex? You really can't. What should you expect to see as you move up in elevation in the mountains today?

  • Lower elevations: Many lower elevation slopes received some rain during this storm. Today's cold front will eventually turn the lower elevation snowpack into a frozen popsicle, but you may be able to trigger wet avalanches while the snowpack is draining and beginning to freeze. Once you climb above the rain line, you'll be dealing with storm slabs and persistent slabs. A professional observer in the Soldier Mountains reported a very sensitive mid-storm layer Tuesday afternoon. Remember that large avalanches releasing in middle or upper elevation terrain can run "full track", impacting lower elevation locations. 
  • Middle elevations: You'll be dealing with the persistent slab avalanche problem described above and dense storm slabs involving the snow from yesterday, last night, and today. Smaller wind slab and loose snow avalanches are very likely and make great triggers for larger slab avalanches. 
  • Upper elevations: Strong wind formed and will continue to build dense, meaty slabs in exposed terrain. The wind-loading will make natural and human-triggered, wind and persistent slab avalanches very likely to occur, and deep persistent slabs (monster 4-8 foot thick slides) are possible. Storm slabs are likely in all very steep, sheltered avalanche terrain. The recent snowfall and wind built large cornices; they could break on their own or with the added weight of a person or snowmobile.   

Be sure to give yourself a large safety margin if you're out playing today. Don't expose yourself to overhead avalanche hazards. Have fun and be safe.

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