19-20

Cornice triggered avalanche north of Mt. Blackmore

Mt Blackmore
Northern Gallatin
Code
HS-ACc-R3-D2-O
Elevation
8700
Aspect
E
Latitude
45.45640
Longitude
-111.01800
Notes

From an email:

We were still hesitant of our results from our snowpit so we decided to cut a cornice that would drop onto the slope below, which I'm estimating to be 40 degrees. We released a cornice that tumbled downslope. The cornice went roughly a quarter of the way downslope before triggering a hard slab avalanche that broke just below the corniced ridgline. The avalanche propagated on both sides of the path and propagated further downslope. The avalanche ran into the flats and flanked in two directions once the slope widened (which I've included in the map below). 
 
We were unable to assess the crown in detail since we weren't comfortable with the amount of hangfire above, but estimate it to be 150 feet wide, running 1000 feet slope distance and roughly 600 vertical feet. The avalanche failed on the persistent weak layer interface that we had doubts about. 
 
 
20200307 @ 12:30pm
Crown:
45.4626N, -111,0219W
8766'
Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Cornice fall triggered by human or explosive action
Trigger Modifier
c-A controlled or intentional release by the indicated trigger
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Wet Snow
Slab Thickness
24.0 inches
Vertical Fall
700ft
Slab Width
150.00ft
Images
Looking down the path of the cornice triggered avalanche
North of Blackmore avalanche path
Map of cornice triggered avalanche
Attached Videos
Cornice triggered avalanche north of Mt. Blackmore - 7 March
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
19-20

Natural wet loose near Cooke and Livingston

COOKE CITY
Cooke City
Code
WL-N-R1-D1.5-G
Elevation
7500
Latitude
45.02020
Longitude
-109.93800
Notes

From email: "[Near Mill Creek] We saw a natural wet slab that had released recently on a nw slope at around 7000’ (WS-N-R1-D1.5-G). Also got a big collapse on a sw aspect at about 7500’ on a moist layer of 4mm depth hoar. HS was only about 50cm where I got the collapse. Overall the snow was some wet hot garbage on all aspects,..."

Separate email: "Photo attached of some wet loose avy activity observed today just west of Cooke City (south aspect, around 8200').  Overall though, minimal wet avalanche activity observed with this significant warm up. No additional slab avalanche activity observed this week,..."

Number of slides
2
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
R size
1
D size
1.5
Bed Surface
G - Ground
Problem Type
Wet Snow
Slab Thickness
18.0 inches
Vertical Fall
150ft
Slab Width
40.00ft
Images
Wet slides out of advisory area
Natural wet loose avalanche in Cooke
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
19-20

Obs from near Mill creek: "...We saw a natural wet slab that had released recently on a nw slope at around 7000’ (WS-N-R1-D1.5-G). Also got a big collapse on a sw aspect at about 7500’ on a moist layer of 4mm depth hoar. HS was only about 50cm where I got the collapse. Overall the snow was some wet hot garbage on all aspects,..." Photo: A. Schauer

Avalanche Details: Natural wet loose near Cooke and Livingston
Out of Advisory Area, 2020-03-07
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    • From e-mail: "...some wet loose avy activity observed today just west of Cooke City (south aspect, around 8200').  Overall though, minimal wet avalanche activity observed with this significant warm up..." Photo: B. Fredlund

    Avalanche Details: Natural wet loose near Cooke and Livingston
    Forecast link: GNFAC Avalanche Forecast for Sun Mar 8, 2020
    Cooke City, 2020-03-07
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