24-25

Avalanches and calm wind in Bridgers

Date

With decent visibility we drove up Bridger canyon to Battle Ridge to look for recent avalanches. The most noteworthy was a slab 500'+ wide, 2'+ deep in Argentina Bowl (photo), and there was an R1-R2 sized debris pile below the Saddle Peak cliffs, but clouds obscured the top of Saddle. There were a few short, small wind slabs that broke along the ridgeline north of Bridger Peak. We also saw a 150' wide storm slab in Truman Gulch (photo).

We looked at the snowpack on the west side of the range in Truman Gulch. In four snowpits HS was 70cm (W, 8200'), 112cm (SW, 8400'), 135cm (NW, 8000') and 140cm (W, 8500'). The two deepest pits had ECTP28 on facets (2mm) 40cm above the ground. The other two had poor structure and soft weak snow in the bottom 30-40cm, but did not propagate in tests. Overall, the snow structure is poor and not trustworthy on the west side of the Bridgers. With more loading we could see big avalanches, whether it's this week, later this month or later in the season, and currently it seems possible a person could trigger a persistent slab avalanche here.

On the ramp there was evidence of yesterday's wind in the form of wind slabs that broke and their debris subsequently drifted over. Today wind was calm to light, and there is plenty of snow to transport if the winds do pick up. A few hours of moderate wind could easily form fresh wind slabs. Snow was starting to fall lightly in the late afternoon.

Region
Bridger Range
Location (from list)
BRIDGER RANGE
Observer Name
Alex Marienthal

Avalanche Airplane Bowl Lionhead

Lionhead Ridge
Lionhead Range
Code
SS-R3-D2-O
Elevation
9300
Aspect
SE
Latitude
44.71450
Longitude
-111.31800
Notes

Riders noted a large avalanche in Airplane Bowl in the Lionhead area. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Slab
Vertical Fall
400ft
Slab Width
600.00ft
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Natural Avalanche North Face Blackmore

Mt Blackmore
Northern Gallatin
Code
SS-N-R2-D2-O
Elevation
9800
Aspect
N
Latitude
45.44440
Longitude
-111.00400
Notes

There was a recent avalanche on the north face of Blackmore. Visibility was poor but it was a small pocket in a steep, rocky zone that broke near the ground. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Slab
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Poor structure on Mt Ellis

Date
Activity
Skiing

Toured up Ellis today. Snow was starting to fall again in the late afternoon. HS varied from fairly thin below 7000 ft to about 110 cm at the top. We found supportable new snow and good skiing. Dug a hand pit at 7500 feet on a NE aspect and found about 50 cm of new snow sitting on facets over a melt freeze crust. At 8300 ft we did an ect on an E aspect and found a similar structure but had no results. 

Region
Northern Gallatin
Location (from list)
Mt Ellis
Observer Name
E. Donahue

Poor test scores up Goose Creek

Date
Activity
Skiing

Big whumph as we stepped up onto the lower meadow to dig a practice pit. Pit was about 75cm deep, NE aspect, looking toward Trail Creek Road. CT12, 3cm from the ground, ECTP 16 on that same weak layer of facets just above the ground.

Region
Northern Gallatin
Location (from list)
Goose Creek
Observer Name
Tom Kochevar