Observation: Alta Periphery 12/29/2011

Observer Name:

Ryan

Observation Date:

12/29/2011

Region:

Salt Lake
Little Cottonwood Canyon
Alta Periphery

Location or Route:

Patsy Marley ridge

Weather

Sky:

Overcast

Precipitation:

Light Snowfall

Wind Direction:

West

Wind Speed:

Moderate

Weather Comments:

Raining to near 8,000' on the way up LCC at ~07:30. On-and-off dense snow/sleet/graupel above that until we left at ~11:00. Cloudy and breezy, with stronger winds on the ridgeline.

Snow Characteristics

New Snow Depth:

New Snow Density:

High

Snow Surface Conditions:

Dense Loose

Damp

Snow Characteristic Comments:

About 3" of new by 10:00, although that may have been as much wind-loading as anything else (some deeper pockets on N-facing). Did not see the rain crust Kobernik reported, although some spots along the ridge had an occasionally-exposed lens-like crust that might have been the same thing. It was mostly covered when we were up there, though. Surface was a mix of dense new snow and graupel, getting more damp as the daytime temperatures warmed.

Red Flags

Wind Loading

Cracking

Red Flag Comments:

Cracking in the upper 2-5" was noted frequently below the ridgeline. Strong winds over the ridge were creating new, dense pillows on the lee side, although several attempts at kicking them did not cause any releasing. Did not observe any collapsing, although we were a little surprised not to see any.

Primary Concern

Primary Concern:

Wind Slabs

Probability:

Moderate

Aspect:

North

Northeast

Northwest

Elevation:

Mid

Trend:

More Dangerous

Primary Concern Comments:

Concern was a combination of the new, dense snow (albeit little) combined with the wind-loading, on top of a mixed bag of weak facets.

snow_profile_location:

Comments - Photos - Videos (group 1)

Dug two pits, one on N-facing at about 9,000 ft and one on N-facing at about 9,800 feet. ECT at the first location was CT23/Q2, second location was CT12/Q2. Second locationwas definitely more wind-loaded, with the new-snow/wind-slab to 6+" and still building when we skied out. Facet mix below the surface at both locations was not pretty. If the wind and precipitation continues throughout the day, I suspect these slabs will be more well-developed by tomorrow.

Observed Danger Rating:

Moderate

Forecast Danger Rating:

Considerable