Touchy storm slabs near WMR

Location Name: Forecaster Observation - WMR accessed backcountry, Whitefish Range Observation date: Saturday, December 30, 2017 - 13:15	Is this an Avalanche Observation: Yes

Observation made by: Forecaster

Location

Tabs

Quick Observation

Touchy storm slab instabilities 8" to 12" thick on previously undisturbed slopes.
Shooting cracks up to 10' long and I skier triggered one soft slab, 10" thick, D1.5 in size.
Numerous slab avalanches ran naturally (or snow plow triggered?) up to D1.5 ran this morning along road cuts enroute WMR or in the Skook Chutes.
Sudden collapse and propagating test results on the 12/15 facet layer, buried 95 cm deep. No other signs of instability on this layer. We probed in several start zones and found this structure is quite variable or absent do to previous avalanching. In some cases, the structure consisted of a few inches of new snow over the Thanksgiving Crust, an indication that all of the snow since then has avalanched away.
Isolated areas had light wind transport

Snowpack, Avalanche, Weather Images:

Snowpack, Avalanche, Weather Videos:

December 30, 2017. Storm slabs and persistent slabs near WMR

Travel Details

Region:

Whitefish Range - Southern (south of Coal Creek)

Route Description:

Terrain adjacent to WMR (Canyon, Skook, etc)

Snowpack Details

Snowpack and Weather Details:

Terrain

Elevation of observation:

5000-6500 ft

Aspect(s) of observation:

Red Flags:

Shooting cracks

More than a foot of new snow or heavy snowfall rates (>1"/hr)

Persistent Weak Layers:

Buried

New Snow in the past 24 hours:

5.00in.

More comments about the snowpack and weather:

On a SW aspect at 5,600 ft. ECTPH, down 95 cm on F hard, 1.5mm facets. ECTN down 30 cm on storm interface (small grained facets). The 12/17 rain crust is unusually thin and soft here (perhaps do to faceting?). The Thanksgiving crust was patchy across the ground, not a continuous layer.

Avalanche Details

Avalanche Details:

Date and Time of Avalanche:

Saturday, December 30, 2017 - 08:15

Avalanche Type:

Soft Slab

Failure Plane/Weak Layer:

Within storm snow

More information or comments about the avalanche:

10" storm slabs failed this morning or last night at all elevations, from 3800 ft to 6,000 ft. Skier triggered one similar slide.

Trigger

Trigger:

natural

Size

Destructive Size:

D1.5

Relative Size:

R2 Small

Crown Height:

Less than 1 ft

Avalanche Location:

Avalanche Forecasts

Tutorials

Observations

Weather

Classes and Events

Videos

Online Resources

Friends of the Flathead Avalanche Center

Flathead Avalanche Center

Touchy storm slabs near WMR

Location

Tabs

December 30, 2017. Storm slabs and persistent slabs near WMR

Call

Contact

In Partnership With

In Partnership With

Avalanche Forecasts

Tutorials

Observations

Weather

Classes and Events

Videos

Online Resources

Friends of the Flathead Avalanche Center

Flathead Avalanche Center

Touchy storm slabs near WMR

Location

Tabs

December 30, 2017. Storm slabs and persistent slabs near WMR

Search

Follow or Subscribe

Call

Contact

In Partnership With

In Partnership With