21-22

Collapses and Whumphs on NE Aspect 8000 feet in Hyalite

Hyalite - East Fork
Northern Gallatin
Code
AF-O
Elevation
8000
Aspect
NE
Latitude
45.45050
Longitude
-110.91900
Notes

From email obs: 12/12/21: "Shooting cracks and whoomphing in wind loaded areas. An approximately 15x30ft wind slab cracked along the bas of a rock band and settled at the base of P2 on high fidelity. Was triggered while traversing along the rock band to gain the second pitch, 1-2 inches of facets on the ground. Wind slab of 6-36in in the gullies."

(Second photo, believed to be from different group, sent on IG)

Number of slides
0
Number caught
0
Number buried
0
Trigger
Foot penetration
Bed Surface
O - Old snow
Problem Type
Wind-Drifted Snow
Images
Cracking drifts in Hyalite
Propagating cracks along top and bottom of windslab
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year
21-22

From obs: 12/12/21: "Shooting cracks and whoomphing in wind loaded areas. An approximately 15x30ft wind slab cracked along the base of a rock band and settled at the base of P2 on high fidelity. Was triggered while traversing along the rock band to gain the second pitch, 1-2 inches of facets on the ground. Wind slab of 6-36in in the gullies." Photo: M. Hearley

Avalanche Details: Collapses and Whumphs on NE Aspect 8000 feet in Hyalite
Forecast link: GNFAC Avalanche Forecast for Mon Dec 13, 2021GNFAC Avalanche Forecast for Tue Dec 14, 2021
Northern Gallatin, 2021-12-12
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    • Taylor Fork

    Date
    Activity
    Skiing

    Heavy wind loading from gusty SW winds and recent snowfall. Made for some touchy conditions.
    This was at 9100’ between Sage and Sunlight basins.

    Region
    Southern Madison
    Location (from list)
    Taylor Fork
    Observer Name
    JR Mooney

    At Lionhead Ridge, strong winds are drifting snow into unstable slabs. On steep rollovers, we observed shooting cracks and one large collapse, or "whumph." With more wind and snow in the forecast, expect conditions to get more dangerous before they improve. Photo: GNFAC

    Avalanche Details: Collapse/ Cracking Lionhead Ridge
    Forecast link: GNFAC Avalanche Forecast for Wed Dec 15, 2021
    Lionhead Range, 2021-12-12
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    • Hyalite Canyon, North of elephant mountain

    Date
    Activity
    Skiing

    Dug a pit on a northeast aspect at 8000’. Performed a CT and ECT. Both collapsed vertically on 26 in facet layer in between base crust and new wind slab. No propagation, no major weak layer failure.

    Region
    Northern Gallatin
    Location (from list)
    Elephant Mountain
    Observer Name
    Harrison Bigos-Lowe

    West Ridge of East Fork -NE Aspect 8000 feet - High Fidelity

    Date
    Activity
    Ice Climbing

    Shooting cracks and whoomphing in wind loaded areas. An approximately 15x30ft wind slab cracked along the bas of a rock band and settled at the base of P2 on high fidelity. Was triggered while traversing along the rock band to gain the second pitch, 1-2 inches of facets on the ground. Wind slab of 6-36in in the gullies.

    Region
    Northern Gallatin
    Location (from list)
    Hyalite - East Fork
    Observer Name
    Matthew Hearley

    Lulu Pass and Republic Creek

    Date
    Activity
    Skiing

    Yesterday (12/11/), we toured around Lulu Pass Area. There was wind effect on almost every aspect. Constant wind, and whiteout gusts happening every 5 minutes or so, we observed the new snow load was being transported everywhere around us. Ended up lapping some low angle meadows.

    Today (12/12), we toured up Republic creek and found roughly 6 inches of low density snow that fell over night without wind which was a nice treat. We dug a pit on a East aspect at 9200 feet and found a stable, right side up snowpack giving us an ECTN. Some small facets were found on the ground but we’re none reactive in our tests. We didn’t find the layered snowpack iv been finding near Bozeman. The cliff faces were shedding some sluff as we got into the alpine.

    Region
    Cooke City
    Observer Name
    Tommy S
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