Public Observation

Observation Details

Signs of Unstable Snow

Observations

Toured and skied lower angle West to North terrain at 6900' - 7600' above yurts (Burn Line to North Corner) Feb 3-6.

Weather: 02/04 - Mostly cloudy, 13-25 F, SSW Lt winds, trace of snow late pm; 02/05 - Overcast, 18-30 F, observed Light N wind (not forecasted), no precip; 02/06 - Clear, 24-39 F, calm to Lt SW winds, no precip

Avalanche problems: Wind slab formation in wind-effected terrain at elevations above 7200', recent Loose Dry avalanches, and a buried weak layer under recent storm snow were all observed in the area.

Snowpack: A near surface facet layer of snow (from the late January high pressure period) can be observed preserved below ~18-30 cm of snow that fell in the area earlier this week. Hand shears and snowpits on all aspects and elevations toured showed evidence of this surface layering above a much more consolidated (1F decreasing to P+) old snowpack. Results from multiple hand shears and compression tests indicated easy to moderate collapse potential of this weak layer below varying slab depths and strength (very soft to moderately dense) on a planar old snowpack surface. However, 3-4 extended column tests on various aspects and elevations did not indicate any propagation potential of the weak layer.
The snow quality was light to dense surface powder that skied very well on lower angle (<30 degrees) slopes, but was showing rapid settlement and warming, especially on southerly-westerly slopes by Sunday (02/06). At least 1' (~25 cm) of snow settlement occurred in the area between Feb 3 and Feb 6. Snow depth on Feb 6th had decreased to ~6.5' (200 cm) in the area.

Overall, great skiing and conditions throughout the weekend!

Snowpit Test results: 02/04
Snowpit #1: 7100', NW aspect, 18 degree slope. Hs = 191 cm;
CT6 (SC) down 25 cm on buried facet layer; CT10 (SC) down 25 cm on buried facet layer
Snowpit #2 - 7100', W aspect; CTM (SP) down 19 cm on buried facet layer; ECTX

Snowpit Test results: 02/06
Snowpit #1 - 6800', W aspect; weak layer observed 19 cm down; ECTX x 2
Snowpit #2 - 7500', W aspect, 18 degree tree-shaded slope; CT 14 (Q1) down 19 cm, ECTN25