Dickey-in around with Wind Slabs

Location Name: 
Foercaster Observation - Marion/ Dickey Creeks
Observation date: 
Saturday, March 9, 2019 - 17:45

Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

Climbed/skied Pt. 7180 between Marion and Dickey Creeks to look for wind slabs. 

  • Triggered 2 small slides that broke less than a foot deep. The debris ran far and fast because of the slope angle. There were tracks adjacent to each slab before a later skier triggered the slabs. Both slabs released on steep slopes (38* +), one on upper-elvation, northerly slope and the second on a mid-elevation, northwest-facing slope.
  • We saw no other signs of instability, and relatively little effect from the southwesterly winds earlier this week. A refrigerator-sized chunk of cornice dropped on a northerly slope produced nothing but sluff and divots.
  • A survey of nearby peaks in ok-but-not-great light showed no other slabs. 
  • 2 thin sun crusts (Tuesday 3/5 and Friday 3/8) exist on steep southerly slopes with sustained sun exposure. They aren't present on any slope with partial shade or more.
  • The 2/2 interface is buried 85 cm below the surface on a southeast facing slope but not reactive in tests.
Snowpack, Avalanche, Weather Images: 
Snowpack, Avalanche, Weather Videos: 

20190309 triggered wind slab2

Travel Details
Region: 
Flathead Range - Middle Fork Corridor
Route Description: 

Essex to Marion Lake, Pt. 7180, descend to Dickey Creek and out

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
SE
S
NW
New Snow in the past 24 hours: 
0.00in.
Total Snow Depth: 
245 cm
More comments about the snowpack and weather: 
Broken skies with a few blue patches in AM. Thicker clouds by early afternoon, with peaks obscured at times. A few light snow showers. Winds mostly calm, with occasional light gusts. Lots of older, firm slab underfoot while skinning up, esp near ridges, but little sign of effects from SW winds. Northerly aprons in Dickey Creek the most wind-affected terrain, with firm, grabby crust. Test profile @6375 ft, SE-facing slope showed snowpack with few layers below top 30 cm. 2/2 interface buried 85 cm below surface (HS245); ECTX, CTX, DT26 RP. Some interfaces in top ~30 cm of snowpack failing w easy or moderate force in ECT, but no propagation.
Blowing Snow: 
None
Wind Speed: 
Calm (No air motion)
Air temperature: 
Below Freezing
Sky Cover: 
Overcast (OVC)
Highest Precipitation Rate: 
Very Light Snowfall (S-1)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Saturday, March 9, 2019 - 14:15
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Old snow
More information or comments about the avalanche: 

Triggered by third skier ski-cutting top of slope. Skier cut across corner of convexity other skiers avoided. His track a few feet from other tracks. 4-10" crown, F at surface, 4F at base of slab. Debris ran far and fast due to slope angle. Nice little powder cloud. 

Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Start Zone Slope Angle: 
42
Aspect: 
North
Starting Elevation: 
7150
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R2 Small
Crown Height: 
Less than 1 ft
Avalanche Length (Vertical Run): 
400ft.
Avalanche Width (Average width): 
60ft.
Hide People Involved
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
Avalanche Location: 
Date and Time of Avalanche: 
Saturday, March 9, 2019 - 18:15
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Unknown
More information or comments about the avalanche: 

Triggered by 4th skier, who drifted just skier's right of previous tracks onto slope less sheltered from wind. Debris ran fast and put up another small powder cloud. Debris soft enough to ski. 

Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Accidentally Triggered
Hide Terrain
Start Zone Slope Angle: 
40
Aspect: 
Northwest
Starting Elevation: 
5800
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R2 Small
Crown Height: 
Less than 1 ft
Avalanche Length (Vertical Run): 
500ft.
Avalanche Width (Average width): 
50ft.
Hide People Involved
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
Avalanche Location: