20-21

Hyalite

Date

Today climbing up at the Nutrcracker we observed extensive scouring occurring in the gullies below the climb. Strong up and downslope winds were pushing snow around, and it wouldn’t surprise me to see drifts in strange places. We were able to get a good look at the terrain in the alpine above Twin and near the Maid, lots of wind transport occurring but no natural avalanches visible.

Observer Name
Sam H

BOttom of Ernest Miller Ridge

Date
Activity
Skiing

60 cm depth
Fist 60-43 cm
knife ~3mm thick (rain crust from the 20th?)
4F - 43-39cm
Fist - 39-0 cm (wonderful garbage)

ECTP 13 @32cm

44.940179, -111.133867
~9100'
SE Flacing Slope
Angle - ~20 degree

Top of the ridge had ~20cm deep coverage with intermittent full ice. Ice that could support human weight w/out skis. Did not find any slabs on the slope. On flats for the entire approach, we experienced ~15 Whoomfs. The crust was noticeably thinner once on slope vs. flats.

We returned 1/3/21 and found an additional 10cm of fresh low-density snow with greater wind affecting and did not venture as high in elevation. A more defined wind slab was found nearing 9400' with obvious signs of high winds from the previous day.

Region
Southern Gallatin
Location (from list)
Ernie Miller Ridge
Observer Name
Kevin Fitzgerald

Cornice triggered avalanche in Divide Basin, Hyalite

Divide Cirque
Northern Gallatin
Code
C-NC-R2-D2
Elevation
9600
Aspect
E
Latitude
45.39340
Longitude
-110.96900
Notes

A backcountry skier wrote, "...observed a fairly large, cornice-triggered avalanche on an east aspect at 9600’ that looked to be several hours old. The crown was 40-100 cm deep, and it looked like it failed about 20 cm into the facets that make up the lower half of the snowpack in this region."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Cornice fall
Trigger
Cornice fall
R size
2
D size
2
Problem Type
Wind-Drifted Snow
Slab Thickness
70.0 centimeters
Weak Layer Grain type
Faceted Crystals
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

A backcountry skier wrote, "...observed a fairly large, cornice-triggered avalanche on an east aspect at 9600’ that looked to be several hours old. The crown was 40-100 cm deep, and it looked like it failed about 20 cm into the facets that make up the lower half of the snowpack in this region."

Northern Gallatin, 2021-01-04

A backcountry skier wrote, "...observed a fairly large, cornice-triggered avalanche on an east aspect at 9600’ that looked to be several hours old. The crown was 40-100 cm deep, and it looked like it failed about 20 cm into the facets that make up the lower half of the snowpack in this region."

Northern Gallatin, 2021-01-04

Divide Basin

Date
Activity
Skiing

I toured up to Divide basin today, and found excellent surface conditions for skiing. There was about 1” of new snow that was being blown around by moderate winds down lower, but the ridgelines looked like they were getting hammered. I experienced one collapse on a low angle, east aspect at 9400’ while ascending an old skin track on my second lap. It looked like a prior party had gotten ECTX in a snow pit nearby, so the little bit of snow has changed things.
I also observed a fairly large, cornice-triggered avalanche on an east aspect at 9600’ that looked to be several hours old. The crown was 40-100 cm deep, and it looked like it failed about 20 cm into the facets that make up the lower half of the snowpack in this region.

Region
Northern Gallatin
Location (from list)
NORTHERN GALLATIN RANGE
Observer Name
Sam Reinsel

From obs: "... in the Crazy Mountains. Observed heavy NE cornicing as well as complex wind transport. Lots of stripped N aspects. Conditions deteriorated throughout the day with high winds and graupel deposition. Our 100cm depth pit was on a 240º SW aspect at 8000 feet, a 20º slope angle,... We performed an ECT and received an ECTX result. We performed a isolated column test and received a CTH - 22 RP Q2, fracturing 30cm below the top on a layer of facets...." Photo: H. Darby

Out of Advisory Area, 2021-01-04