Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

The combination of recent snow, wind, and buried weak layers make human triggered avalanches possible today. Monitor the wind direction as well as the influence of the sun and pay attention to signs of instability such as cracking within settled and drifted snow or audible collapsing of the snowpack. Steep and rocky areas that have been affected by the wind or the sun over the last week are the most likely areas to trigger a slab.

 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2.5

    Weak, sugary snow is buried 1-3 feet deep below the surface of the snow. At the upper elevations these weak layers could be buried in excess of 4 feet. These layers formed from cold, dry periods that occured in November and early December and are widespread. Avoid steep and rocky areas that are wind effected where triggering a slab is more likely. Be mindful of the sun and its influences on the snowpack today. Snow sufaces could become damp with the warm temperatures and high clouds today and free water could percolate down through the snowpack.

    A layer of surface hoar is also present in the top 3 feet of the snowpack in many areas that are sheltered from dramatic winds. Dig down into the snowpack to find this thin grey stripe. 

    Avalanche paths that have slid earlier in the season are suspect as new slab depths increase with each successive snowfall. 

    (1/5/2023)

    This avalanche was triggered by a rider at Jack Hollow on a southeast aspect at 9,500 feet.  It failed on weak snow in the lower half of the snowpack and was approx. 3 feet thick. 

    Photo: Antonioli

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Wind slabs/storm slabs (both soft and hard) are possible at the upper elevations today, with depths from 1-1.5 feet. These are most likely on NW through S aspects. 

    Up to 15 inches of snow has fallen at the upper elevations in the Greys zone over the last 3 days. Monitor the wind direction and look for blowing and drifting snow.

    A melt freeze crust is present on the windward side of the ranges such as the Salts or the Palisades. This crust exists up to 9000' and could provide a slick sliding surface for the newly settled snow from January 11/12. 

    The new snow could also form into very shallow surface slabs just from settlement and the influence of the sun today. Be mindful of roller balls and other signs of instability in very steep southerly terrain. 

    (1/11/2023) Photo: Carus

Avalanche Discussion

Weather Synopsis

Currently western Wyoming is sitting under a ridge of high pressure with some moisture aloft. This will bring warm temperatures with high clouds, causing a greenhouse effect. 

A deep trough that eventually closed off north of the Texas Panhandle dropped 12-15 inches of snow with over an inch of SWE in the Tetons and the Greys zones on January 11/12. Togwotee received closer to 6-8 inches of snow with this system. 

Prior to that WSW flow with imbedded Pacific moisture impacted the forecast area with 3-7 inches of snow and breezy conditions on January 9/10.

Recent Avalanches

 A human triggered avalanche was reported on January 5th from the Middle Fork of Piney Creek on the east side of the Wyoming Range (see observations). 

  • Middle Piney Creek- 20230105, SS-ARu-D2-O, SE aspect @ 9500'

A notable natural avalanche cycle followed on the heels of tropical moisture in a SW-W flow that hit western Wyoming from December 27- January 1.

Snowpack Summary

Current snow surfaces are composed of medium density snow that has settled from the January 11/12 storm. In wind affected areas the surface of the snow has turned into upside down wind slabs. 

Snow depths are approaching 1.5-2 meters at upper elevations in the Greys forecast zone. The top half of the snow pack is composed of new, decomposing, and wind packed snow with some layer of buried surface hoar mixed in for good measure. The bottom half of the snowpack is composed of crusts and advanced facets that are around 2mm in diameter in some locations.  

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