22-23

Small wind slab avalanche, Cooke

Lulu Pass
Cooke City
Code
SS-NC-R1-D1-O
Aspect
SE
Latitude
45.07090
Longitude
-109.95800
Notes

We skied on the knob Saturday and Sunday. Dug a pit on the east facing slope just above the steeper roll over. ECTX. No result. Minimal wind loading next to the tree bands. We skied the slope 20+ times (between 4 skiers). 

We took the sled up track around the north side of the knob and below the avy debris from the slide triggered a last week. Only sign of avalanche activity (other then the obvious one) was a small wind slab release on a south facing slope near the top of the pass. Marked on the map below. Photo attached is of the previous slide but the wind slab release would be where the red X is if the photo continued. Looked to be 30ft across, ran for 15-20ft and about 6inches deep. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Cornice fall
R size
1
D size
1
Bed Surface
O - Old snow
Problem Type
Wind-Drifted Snow
Snow Observation Source
Small wind slab avalanche
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
22-23

Getting weak, but not unstable...yet

Date
Activity
Skiing

We skinned up Tylers and ran into a group of 4 who just wrapped up digging a pit. They had ECTP18 on the facets at 50 cm (HS 90 cm). We skied into Bear Basin in the Spanky’s area. We dug a pit that also had HS 90 cm. A few ECTNs but nothing concerning other than the thick layer of facets near the ground. Weak but not unstable…yet. The snowpack story seems more similar than not from West Yell to the Bridgers and Cooke. This layer of 2-4mm facets will be an issue with the next decent load, but until then the weakening continues.

Region
Northern Madison
Location (from list)
Beehive Basin
Observer Name
Doug Chabot

Small, cornice triggered avalanche, Beehive

Beehive Basin
Northern Madison
Code
SS-NC-R0-D1-O
Elevation
9000
Aspect
E
Latitude
45.32570
Longitude
-111.38000
Notes

Today we toured up Beehive Basin to Prayer Flags and down into Bear Basin. We found moderate winds transporting snow at Prayer Flags. We also observed a recent small natural avalanche that broke just below the cornice at prayer flags (9200'). It was unclear if a cornice collapse triggered the avalanche. We did not go to the crown, but estimated it to be about 20-30 feet wide, 6-8 inches deep, and running less than 100 feet (Photo attached).

During our tour we saw lots of pillows of wind drifted snow and locations where slabs of wind drifted snow collapsed and cracked under our skis. 

In Bear Basin we dug a pit and found weak faceted snow on the ground. We did not have any significant test results, but the structure along with the wind and recent avalanche activity was enough to keep us off steep slopes for the day. 

The snow surface was powder in protected places, breakable wind crust in others, and either scoured or wind board at ridge lines.The skiing was best on low angle slopes protected from the wind. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Cornice fall
R size
0
D size
1
Bed Surface
O - Old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
6.0 inches
Vertical Fall
100ft
Slab Width
30.00ft
Images
West Face of Bear Basin Profile
Small, cornice triggered avalanche
Snow Observation Source
Small, cornice triggered avalanche
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
22-23

Today we toured up Beehive Basin to Prayer Flags and down into Bear Basin. We found moderate winds transporting snow at Prayer Flags. We also observed a recent small natural avalanche that broke just below the cornice at prayer flags (9200'). It was unclear if a cornice collapse triggered the avalanche. We did not go to the crown, but estimated it to be about 20-30 feet wide, 6-8 inches deep, and running less than 100 feet. Photo: J. Breen

Avalanche Details: Small, cornice triggered avalanche, Beehive
Forecast link: GNFAC Avalanche Forecast for Wed Dec 21, 2022GNFAC Avalanche Forecast for Thu Dec 22, 2022
Northern Madison, 2022-12-21
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    • Small, cornice triggered avalanche

    Date
    Activity
    Skiing

    Today we toured up Beehive Basin to Prayer Flags and down into Bear Basin. We found moderate winds transporting snow at Prayer Flags. We also observed a recent small natural avalanche that broke just below the cornice at prayer flags (9200'). It was unclear if a cornice collapse triggered the avalanche. We did not go to the crown, but estimated it to be about 20-30 feet wide, 6-8 inches deep, and running less than 100 feet (Photo attached).

    During our tour we saw lots of pillows of wind drifted snow and locations where slabs of wind drifted snow collapsed and cracked under our skis. 

    In Bear Basin we dug a pit and found weak faceted snow on the ground. We did not have any significant test results, but the structure along with the wind and recent avalanche activity was enough to keep us off steep slopes for the day. 

    The snow surface was powder in protected places, breakable wind crust in others, and either scoured or wind board at ridge lines. The skiing was best on low angle slopes protected from the wind. 

    Region
    Northern Madison
    Location (from list)
    Beehive Basin
    Observer Name
    Jackson

    Poor Structure above Hebgen Lake

    Date
    Activity
    Skiing

    We dug a pit on a SE facing hill at 9,000 feet above Hebgen Lake. We had no signs of instability on the trip up. Near the ridgeline we dug and tested the 85cm snowpack and got an ECTP26 at the interface of the F- weak facets and slab of snow above. The structure was poor, but the snow was relatively stable. It would be possible to trigger a slide in an area where the snowpack is thinner and weaker, and I expect instability to increase with more snowfall.

    Region
    Lionhead Range
    Location (from list)
    Hebgen Lake
    Observer Name
    Doug Chabot
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