Northern Gallatin

Natural Wet, Loose Avalanches Hyalite

Hyalite - main fork
Northern Gallatin
Code
WL-N-R1-D1-I
Latitude
45.44720
Longitude
-110.96200
Notes

Today in Hyalite there was roughly 5" new snow. It quickly lost cohesion when the sun came out and many size 1 dry and wet loose came off of steep rocky areas. I did not observe anything larger. Yesterday I observed a cornice fall on an E aspect of Mt. Bole around 9500 ft that probably occurred on 3/6. It ran several hundred meters downhill, entrained some surface snow, and appeared to trigger a size 2 slab when it encountered steeper terrain. That being said I was at G1 so I didn't really get a good look at it.

Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Slab Thickness
5.0 inches
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
19-20

Natural Dry, Loose Avalanches on Blackmore

Mt Blackmore
Northern Gallatin
Code
L-N-R1-D1-I
Elevation
9800
Aspect
E
Latitude
45.44450
Longitude
-111.00200
Notes

Dry loose avalanches on Blackmore. The snow stayed surprisingly cold and dry throughout the day.

Number of slides
4
Number caught
0
Number buried
0
Avalanche Type
Loose-snow avalanche
Trigger
Natural trigger
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Images
Dry, loose natural avalanches on Blackmore
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
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
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