23-24

Two Avalanche’s within a few hundred yards

Date
Activity
Snowmobiling

No details, came upon them while riding and making observations of the terrain. One was North-Northeast, the other was North-Northwest facing. Across the drainage from each other. 
Also, notice three other small avalanches on a west facing slope, about two miles east of the first two. All five were on slopes well over 30. In the centennial mountains, close to the continental on the Idaho/Montana border. 

Region
Island Park
Location (from list)
Centennials - Idaho

Beehive/Bear Obs.

Date
Activity
Skiing

We took our level 1 course up to the ridge between Beehive and Bear Basin. Skies oscillated between overcast and broken as light snow fell throughout the day with little to no accumulation. Winds were generally light, and no snow was being actively transported.

We descended a low angle east aspect down to about 8500' and found quality surface conditions and fun turns.  This week's snow comprised the upper 35 cm of the snowpack, was right side up, and generally well-bonded to the new/old interface below. Hand shears, up-track tests, and small test slopes were non-reactive.  We avoided any sustained slopes over 30 degrees and we saw no obvious signs of instability during our tour.

We dug two quick pits and performed an ECT in each. We found very similar poor structure in both pits and both ECT's propagated across the column within a layer of soft facets about 18" below the surface.

 

East aspect @ 8500', 28 degree slope

HS 90 - ECTP24 @ 44 cm 

90-55  F>4F>1F - This week's snow

55-50 - P - Rounded Grains -  January snow

50-35 - F - Facets

35-33 - 4F - Decomposing Crust/Facets

33-20 - F - Facets

20-Gnd - 1F - DH/Facets

 

 

East aspect @ 9100', 12 degree slope

HS 88 - ECTP11 @ 43 cm within a layer of fist-hard facets

Very similar structure to above, except for a 2 cm pencil hard MFcr at the interface below this week's snow capping a few cm of pencil hard rounds from January.

Fist-hard facet layer began at 47 cm and transitioned to 4F DH at 20 cm, with large and striated crystals visible to the naked eye.

 

Region
Northern Madison
Location (from list)
Bear Basin
Observer Name
Josh Lipkowitz

Natural avalanche on Mt. Republic, Cooke City

Mt Republic
Cooke City
Code
SS-N-R3-D2
Elevation
8900
Aspect
N
Latitude
45.00170
Longitude
-109.95500
Notes

From email: "Natural avalanche from yesterday evening or last night.  

North facing aspect, with an interesting 3 tiered crown beginning around 8900'."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
3
D size
2
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year