Long sluffs and small slab formation in Cascadilla Creek

Location Name: 
Forecaster Observation - Cascadilla Creek, Flathead Range
Observation date: 
Sunday, December 17, 2017 - 13:45

Is this an Avalanche Observation: 
No
Observation made by: Forecaster

Location

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Quick Observation

Snowpack summary: Snowpack was similar to what we've been seeing throughout the advisory area. We found that overall surface conditions were highly variable throughout our tour; some places had a thin new rain crust, some had a punchy 1" wind slab, while others were dense new snow. We triggered a small soft slab on a small test slope while ascending the north side off the drainage. Slab consisted of dense, wind loaded snow deposited on top of our weak cohesionless snow that formed during the high pressure spell. We didn't see a lot of surface cracking but felt that our small test slope gave us bulls eye data to not venture onto wind exposed slopes with similar slope aspect (NE). We produced numerous skier triggered loose dry avalanches on wind sheltered slopes greater than 35 degrees. The last one ran close to 800 vertical feet down to the creek. All loose dry avalanches were easy to manage while skiing but moved extremely fast and could easily push a skier around who's not paying attention. Otherwise, lower angled, wind sheltered slopes skied the best.

Weather summary: Low cloud deck obscuring mountain tops, light snow (S -1)/ freezing rain, and overall light to calm winds. On ridgetops, winds were light and out of the SW while nearly calm down in the creek bottom.

Avalanche conditions: No natural avalanches visible today.

Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Flathead Range - Middle Fork Corridor
Route Description: 

Traveled up Cascadilla Creek two-track and then into the basin proper via main summer trail route.

Activity: 
Skiing
Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation: 
N
NE
Red Flags: 
Shooting cracks
Persistent Weak Layers: 
Buried
New Snow in the past 24 hours: 
2.00in.
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Sunday, December 17, 2017 - 13:00
Avalanche Type: 
Loose Dry/ Sluff
Failure Plane/Weak Layer: 
New/old snow interface
More information or comments about the avalanche: 

Skier triggered loose dry avalanches that were generally small but ran fast and far. The last one triggered ran approx. 800 vertical feet down to the creek bottom.

Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Start Zone Slope Angle: 
35
Aspect: 
Northeast
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R1 Very Small
Avalanche Length (Vertical Run): 
800ft.
Hide People Involved
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0