22-23

Ski Triggered Avalanche

Date
Activity
Skiing

From IG: “Ski cut trigger. West facing. 9800ft. Big sky area.”

Region
Northern Madison
Observer Name
Isaac Freeland

Natural Avalanche, 2nd Yellowmule

Buck Ridge
Northern Madison
Code
SS-N-R2-D2-I
Elevation
9400
Aspect
NE
Latitude
45.17190
Longitude
-111.38000
Notes

We rode through First and Second Yellowmule at Buck Ridge. There was a natural avalanche below the cornice line on the headwall above second Yellowmule that broke within the last 12 hours as it was not covered by any new snow. From a distance, it looked ~200' wide and broke 1-3' deep. I believe it failed under the storm snow, not of deeper weak layers.

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
I - Interface between new and old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
24.0 inches
Vertical Fall
75ft
Slab Width
200.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Natural Avalanches, Bridger Range

BRIDGER RANGE
Bridger Range
Code
N
Latitude
45.85120
Longitude
-110.94800
Notes

From Marienthal Observation: "Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station. It was 75’ wide, 1-1.5’ deep and 25’ vertical. HS-N-R4-D1.5/2. It was on an east facing slope, south of the long slope that has cornices. The slope with cornices hadn’t slid at this point. On the way home at 3:30 the larger slope with cornices had slid. It was very big, possibly R5. 1.5-2’ deep, 200’ wide, huge chunks of hard slab and cornice. Looks like new wind-loaded snow with some gouges into older snow.

From Olson creek I had a cloud-free flat light view of the ridge from Saddle to Bridger Peak and looked with binoculars. There was a wind slab just north of quarter saddle that did not go over the cliffs. Probably 1-2’ deep, 30’ wide of new snow. There was a large wind slab on the north half of Between the Peaks (250’ wide) and one similar depth wind slab in the Pinnacles (100’ wide). Both of these broke 1-3’ deep immediately below the cornice and did not entrain much snow or propagate very wide or downslope given how much new snow there was. I could see the debris from the slide between the peaks which ran over 1000’ vertical to the top of the runout zone but relatively low volume."

Number of slides
5
Number caught
0
Number buried
0
Trigger
Natural trigger
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

From email, "At 12:45 I saw Climax run naturally. SS-N-R2-D2-I. The low visibility and distance made it hard to tell how deep the crown was, but based on there not being much volume of debris and it not running very far, I’m guessing it was within the new snow/storm interface and didn’t step down to any buried PWL.
In the photo, the red shows the approximate crown line, blue shows debris."

Cooke City, 2023-02-21

Climax Path, Natural Avalanche

Woody Ridge
Cooke City
Code
SS-N-R2-D2-I
Elevation
9900
Aspect
E
Latitude
44.97390
Longitude
-109.92400
Notes

From email, "At 12:45 p.m. I saw Climax run naturally. SS-N-R2-D2-I. The low visibility and distance made it hard to tell how deep the crown was, but based on there not being much volume of debris and it not running very far I’m guessing it was within the new snow/storm interface and didn’t step down to any buried PWL."

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
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Natural Avalanche, Wall Mountain

COOKE CITY
Cooke City
Code
N-D2.5
Aspect
N
Latitude
45.02020
Longitude
-109.93800
Notes

Residents of Silver-Gate caught a glimpse of a large natural avalanche south of Silver Gate on Wall Mountain. The size is uncertain, but it knocked down a stand of trees. Two people state that they believe they heard the avalanche in the pre-dawn hours. 

Number of slides
1
Number caught
0
Number buried
0
Trigger
Natural trigger
D size
2.5
Problem Type
New Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station. It was 75’ wide, 1-1.5’ deep and 25’ vertical. HS-N-R4-D1.5/2. It was on an east facing slope, south of the long slope that has cornices. Photo: GNFAC

Bridger Range, 2023-02-21

Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station... The slope with cornices hadn’t slid at this point. On the way home at 3:30 the larger slope with cornices had slid. It was very big, possibly R5. 1.5-2’ deep, 200’ wide, huge chunks of hard slab and cornice. Looks like new wind-loaded snow with some gouges into older snow. Photo: GNFAC

Bridger Range, 2023-02-21

Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station... The slope with cornices hadn’t slid at this point. On the way home at 3:30 the larger slope with cornices had slid. It was very big, possibly R5. 1.5-2’ deep, 200’ wide, huge chunks of hard slab and cornice. Looks like new wind-loaded snow with some gouges into older snow. Photo: GNFAC

Bridger Range, 2023-02-21