24-25

Storm instabilities in Middle basin

Date
Activity
Skiing

Skied into middle basin from Beehive this morning and found 8-12 inches of unconsolidated snow on top of a sun crust. While skinning back up to the Beehive/Middle ridge we remotely triggered 12 inches of storm snow on a SE facing gully from 15 ft away, the crown was ~50 ft long. ~8,200 ft. 

Winds increased throughout the morning, actively loading E aspects. 

Region
Northern Madison
Location (from list)
Middle Basin
Observer Name
J Nadison

Small skier triggered wind slab in N Madisons

NORTHERN MADISON RANGE
Northern Madison
Code
SS-ASu-R1-D1-I
Latitude
45.29520
Longitude
-111.41000
Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
8.0 inches
Vertical Fall
10ft
Slab Width
10.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Woody Rige, ECTN's on 2mm SH

Date
Activity
Skiing

We skied east and west aspects of Woody Ridge today.  It was snowing most of the day, with periods of heavy snowfall, which accumulated to about 4-5" of fresh throughout the day.

We found buried surface hoar in 3 different snowpits, on east and west aspects, between 9300-9700'.  In each place the SH was buried under about 25cms of new snow, and I would describe it as somewhat irregular/ inconsistent, and mixed with some other faceted snow types.  The SH crystals were generally about 2mm in size.

In our snowpit (file attached) at 9550', west aspect, HS 70, we had an ECTN12 at 45cms. (on that surface hoar layer).

No collapsing, no cracking.  No avalanche activity observed (low vis).

One additional note was that slopes exposed to the SW wind had a thin rime crust that appears to have formed last night.  The ridgeline was also noticeably rimed.  In areas this rime crust was up to 1cm thick and 1F hardness.  We were not finding this rime crust on leeward or sheltered slopes.

 

 

Region
Cooke City
Location (from list)
Republic Creek
Observer Name
B. Fredlund

Shooting cracks in Middle Basin

Middle Basin
Northern Madison
Code
Latitude
45.33740
Longitude
-111.38100
Notes

When skiing into middle basin, I stopped at the top of a convex roller and had cracks shooting out 50 feet in either direction from what seemed to be a soft slab in the new snow that slid about a foot or so. This was the most major sign of instability from the day. Lots of shooting cracks when skiing and skinning in the new snow. 

Number of slides
0
Number caught
0
Number buried
0
Problem Type
New Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year

Windslab above surface hoar near W. Yellowstone/IP

Two Top
Island Park
Code
SS-AMu-R2-D1-O
Latitude
44.61040
Longitude
-111.30300
Notes

Small windslab triggered on approach for inspection. Failure interface had 5 mm Surface Hoar. Soft slab, remote propagation onto the adjacent slope. Debris covered about half of the road bed.

Number of slides
2
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
2
D size
1
Bed Surface
O - Old snow
Problem Type
Persistent Slab
Slab Thickness
10.0 inches
Vertical Fall
20ft
Slab Width
50.00ft
Weak Layer Grain type
Surface Hoar
Weak Layer grain size
5.00mm
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year