No signs of instability on Lost Johnny

Location Name: Forecaster Observation - Lost Johnny, Swan Range Observation date: Tuesday, December 26, 2017 - 13:00	Is this an Avalanche Observation: No

Observation made by: Forecaster

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Quick Observation

Stronger snowpack here than what we've observed recently in other parts of the forecast area
~3 feet of recent snow over the 12/17 rain crust (1 cm thick, ice hard) above rounding facets over the faceting Thanksgiving crust (see profile). The snowpack was generally deeper and stronger at higher elevations. We did not get any propagating results at multiple test locations, nor observe any collapses or cracking
The previous cycle produced slides up to D2 on specific terrain features; not widespread here.
Small grained near surface facets and surface hoar on the snow surface.

Snowpack, Avalanche, Weather Images:

Travel Details

Region:

Swan Range - East Side (Hungry Horse Reservoir access)

Route Description:

Up Lost Johnny Road to the Lost Johnny play area, to an elevation of 6,300 ft.

Activity:

Snowmobiling

Snowpack Details

Snowpack and Weather Details:

Terrain

Elevation of observation:

3500-5000 ft

5000-6500 ft

Above 6500 ft

Aspect(s) of observation:

Persistent Weak Layers:

On the surface

Buried

New Snow in the past 24 hours:

0.00in.

Total Snow Depth:

225 cm

More comments about the snowpack and weather:

Two test pits, one at 6,300 ft, NW aspect, the other at 4800 ft, E aspect showed a similar snowpack structure and did not produce any noteworthy test results. The 12/15 facet layer is slightly larger and weaker at the lower elevation pit site.

Avalanche Details

Avalanche Details:

Date and Time of Avalanche:

Tuesday, December 19, 2017 - 17:00

Avalanche Type:

Soft Slab

Failure Plane/Weak Layer:

Unknown

More information or comments about the avalanche:

Slides from 12/19 cycle on various aspects, mostly above 5500 ft.

Trigger

Trigger:

natural

Terrain

Starting Elevation:

above-treeline

Size

Destructive Size:

D2 Could bury, injure, or kill a person.

Relative Size:

R2 Small

Avalanche Location:

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No signs of instability on Lost Johnny

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No signs of instability on Lost Johnny

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