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 and pay attention to signs of instability such as cracking within drifted snow or audible collapsing of the snowpack.

Yesterday a snowboarder was caught and carried in a persistent slab avalanche on the east side of the Wyoming Range. Similar events are possible today.  

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. 

    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. 

    (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 (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 you 6 inches of snow has fallen at the upper elevations in the Greys zone over the last 3 days. This snow has largely been low density and is readily available for transport. Monitor the wind direction and look for blowing and drifting snow. 

    (1/2/2023)

    Cornice failure and subsequent small soft-slab avalanche on anE aspect at 8000' in the Snake River Range.

    Photo: Antonioli

Avalanche Discussion

Weather Synopsis

The Tetons have picked up 2-5 inches in the last 24 hrs, with the Greys picking up around an inch and Togwotee receiving an inch or less. Winds have been light to moderate at ridgline, with average speeds in the 10-15 mph range and directions out of the S through W. In the last 3 days the mountains of western Wyoming have picked up 6-16 inches of snow with light to moderate winds.

A weak trough began to impact western Wyoming on January 5th (yesterday). Prior to this the forecast area was under primarily NW flow as a closed low system sat over southern Minnesota.

A pacific low pressure system will push a weak and dirty ridge over the forecast area Friday night into Saturday morning. The next pulse of moisture looks to be showing up  Sunday night into Monday ahead of a larger trough.

Recent Avalanches

The most recent natural avalanche cycle followed on the heels of tropical moisture in a SW-W flow that hit western Wyoming from December 27- January 1. A human triggered avalanche was reported yesterday from the Middle Fork of Piney Creek on the east side of the Wyoming Range (see observations). Luckily everyone is ok.

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

Snowpack Summary

Current snow surfaces are composed of low density snow that has settled with some graupel from January 5 mixed in. 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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