Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avoid steep slopes with wind drifts or stiff snow on the surface to reduce the chances of triggering an avalanche. Although not likely,  triggering a large, destructive avalanche breaking deeper in the snowpack remains a possibility. Safer conditions—and the best skiing and riding—can be found on gentler slopes sheltered from the wind.

Conditions are more dangerous near the Smoky Mountain crest/Dollarhide Summit where the recent storm hit the hardest. Refer to the Galena Summit & Eastern Mtns Forecast if you're traveling in this area.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    The past 5 days dropped 12-30" new snow in this zone, with the greatest amounts falling near Dollarhide Summit. Strong winds accompanied much of this snowfall. Despite lower snow totals around the Wood River Valley, small, natural, and skier-triggered avalanches were reported above the Wood River Valley on Wednesday and Thursday. Yesterday saw another bout of strong, gusty W winds with the passage of a cold front that marked the end of this extended storm cycle. On Titus Ridge yesterday, I observed large quantities of snow being transported by the wind (watch the video above/right).

    Wind slabs will be more common at upper elevations, but this week's wind also drifted some open middle and lower elevation terrain (example). Triggering a wind slab is most likely near ridgelines, beneath cornices, and on the sides of cross-loaded gullies. Avoid slopes steep enough to slide where you see evidence of wind loading such as drifted, pillowed areas,  or feel denser/stiffer snow beneath your board(s) or sled.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    A mix of facets and crusts leftover from October snowfall make up the base of the snowpack on most shady middle and upper elevation slopes. Some sunnier, upper elevation aspects have this layer too. The recent storm event just added a huge load to this weak layer, especially on wind-loaded slopes. You'll now find this weak snow buried anywhere from 2-5+' deep—it'll be the most deeply buried near Dollarhide Summit southwest to the Soldiers. In fact, the Dollaride area may be a "sweet spot" due to a combination of a particularly weak October snow and significant recent loading.

    Most savvy backcountry skiers and riders have chosen to avoid steep slopes where this old snow exists, and that strategy will remain a prudent one in the wake of this recent loading event. This is not a tough strategy to swallow given the excellent riding and skiing conditions on slopes lacking the old October faceted snow.  

    (1/2/2022) This large persistent slab avalanche was observed above Corral Creek, near Johnstone Peak. It failed on a N/NW facing slope at 8,600'. The terrain and trees below the crown limited its size, but the crown is over 500' wide.

Avalanche Discussion

Pardon my enthusiasm, but the last month has been mind-blowing. Since December 11th, we've had three separate multi-day storm events that each dropped 2-4+" of SWE (snow water equivalent). Not to mention additional "dribs and drabs" between these storms. Back on December 10th, things were grim and our snowpack was hovering around 60-80% of average. Fast forward...in less than a month, we're now at 140-160% of normal. 

Accurately measuring snowfall is tough, especially during multi-day storm events. The only way to do it with any reliability is to have a live human checking a snow stake daily. Any volunteers? Remote weather station snow sensors measure both snow height gain (snowfall) and snow height loss (settlement). Both of these processes happen simultaneously during big storms—hence the inaccuracy. One thing we can do is look at the amount of SWE that's accumulated over a given timeframe, and using an average snow density, we can come up with an estimate of snowfall. For the calculations, I use an 8% average density which seems reasonable (and likely conservative) given the colder temperatures we've had over the past month. Here is the estimated snowfall since December 11th at a handful of stations:

  • Banner Summit: 150”
  • Vienna Mine: 180”
  • Galena Summit: 130”
  • Dollarhide Summit: 145”
  • Baldy: 100”
  • Hyndman: 85”
  • Soldier Ranger Station: 100”

I suspect that for a number of our stations, this was record-setting snowfall!

These storms have produced rapidly-changing conditions that can be difficult to track. As we head into the first period of extended high pressure since these storms began, it'll be beneficial to see what avalanches occurred where, fit this information into our theories of snowpack stability, and see where that leaves us. Stay tuned!

Be sure to catch up on the week's conditions in Chris' latest Weekend Update.

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