Unstable hard wind slabs in the Bridgers

Unstable hard wind slabs in the Bridgers

Date
Activity
Skiing

Toured up the Ramp in the Bridger Range. At the top of The Ramp/Wolverine I pushed on some small wind-loaded terrain features with skis. About three inches of soft snow moved/cracked no wider than my ski width, then one step lower a hard slab cracked out about 10' wide, 10-12" deep and did not move more than a few inches downhill due to flatter terrain supporting it below. The slab was pencil hardness which leads me to believe it was older than the last snowfall on Wed-Thurs, but possible it formed during that event if there was a period of moderate-strong wind at the ridge. I had two other terrain-feature sized "whumphs" on similar small wind-loaded slopes directly adjacent. These hard slabs were sitting on sugary facets, and show that avalanches can be triggered on previously wind-loaded slopes. While these were small, a similar size slab on a steeper slope could easily take you for a ride, and larger avalanches are possible on larger wind-loaded slopes.

Warm temps made the recent snow moist and denser, feeling more like a slab, but there was not quite enough recent snow on non-wind loaded slopes to get much cracking or propagation in tests. There were small cracks on the surface, but did not travel beyond shovel or ski width. A pit at 8,300' on a northeast aspect showed a very weak snowpack with generally stable test scores. and we had ECTX and ECTN results, a PST 35/100end at 30cm above the ground, and PST 25/100slab-fracture below the recent snow at 63cm above the ground. Snow depth was 75-85cm.

There were natural rollerballs on most aspects initiated from warm snow falling off trees. Possible recent small-medium slab avalanche (8-12" deep) on the west side, behind the Patrol lift, but didn't get a great look. There were rollerballs on that slope which may have triggered a slab?

Temperatures were above freezing and it was raining below 8,000' at 10am. Snowing above 8000' briefly, accumulated to 1cm. Calm wind. Partly sunny by mid-afternoon. Skins were glopping bad off the heavily used skin tracks, and moist snow surface will become a melt-freeze crust on most aspects, possibly with the exception of a few slopes at the highest elevations.

Region
Bridger Range
Location (from list)
The Ramp
Observer Name
Alex Marienthal