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Sperry
Location Name:
Forecaster Observation - Sperry, GNP
Observation date:
Sunday, December 16, 2018 - 15:30
Is this an Avalanche Observation:
No
Observation made by:
Forecaster
Tabs
Quick Observation
Signs of instability included isolated cracking underfoot and collapsing (several).
An upper elevation snowpit revealed a buried faceted layer below the recent new snow. Propagation occurred on this layer with easy force (ECTP 4)
Warm humid conditions contributed to natural and easily triggered rollerballs in the surface snow.
Sticky surface snow was our nemesis while breaking trail and on our descent.
Snowpack, Avalanche, Weather Images:
Snowpack, Avalanche, Weather Videos:
December 16, 2018 - Sperry snow structure
Video of December 16, 2018 - Sperry snow structure
Travel Details
Region:
Glacier National Park - McDonald Lake Area
Route Description:
Up the Gunsight Pass trail.
Snowpack Details
Snowpack and Weather Details:
Terrain
Elevation of observation:
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation:
N
S
W
NW
Red Flags:
Collapsing / whumpfing noises
Rollerballs / pinwheels
Persistent Weak Layers:
Facets or Faceted Crust
Buried
New Snow in the past 24 hours:
1.00in.
Total Snow Depth:
35
More comments about the snowpack and weather:
Still a thin snowpack at all elevations. We dug a snowpit at 6900' on a wind-loaded north aspect. HS=100. One faceted layer 12" below the surface produced propagation ECTP 4. At the bottom of the pit, the Thanksgiving crust was capped with 25 cm of weak faceted snow. The remainder of the pit was wind slab and recent snow. At middle elevations, the snow surface became moist and sticky by mid-morning.
Wind Speed:
Light (Twigs in motion)
Wind Direction:
Southwest
Air temperature:
Below Freezing
Snow line:
6000'
Sky Cover:
Mostly Cloudy (BRK)
Avalanche Details
Avalanche Details:
Date and Time of Avalanche:
Sunday, December 16, 2018 - 20:30
