Tricky to find Surface Hoar

Location: Crested Butte Area
Date of Observation: 01/22/2017
Name: Evan Ross

Subject: Tricky to find Surface Hoar
Aspect: East, South West, West
Elevation: 9,500-10,700

Avalanches: Intently skier triggered several D1s on westerly aspects at 9,500ft. Slabs pulled back to slope angels of about 35 degrees. Propagated about 10 to 30 feet wide in small terrain above a drainage.

Good views of the peaks around the area. No other recent avalanche observations. Other then some previous loose snow avalanches from last week.
Weather: Clear skis east of Paradise Divide, became overcast in the afternoon. Calm winds with a few snow plums off random high peaks. Sun was warming snow surfaces.
Snowpack: On the January 19th surface hoar hunt. Surprisingly , mostly didn’t find it where expected. Multiple pits on 25-35 degree, easterly aspects had little for layers of concern in the upper snowpack. Test showed some failures within the storm snow, but not much for persistent grains at the 1/19 snow interface. Further expected to find it on some northeasterly rolls, but similar results as above. Some pits in the area had small NSF at the area, but these were random and isolated. This was open terrain to down valley winds. Maybe the SH had been blown away?

One pit on a more protected norther easterly aspect at 10,500ft had the surface hoar present. The SH wan’t visible in clean pit walls and column tests where needed to identify the layer. The snow above was still very soft and about 40 cm thick.

The only more obvious sings to instability was on collapsible crusts or facets on crusts. South easterly slopes had a thing and soft crust that was producing muffled collapses while traveling through the terrain. Small facets where below this crust. The most notable results where westerly slopes at 9,500ft that had small facets on a thin soft crust. Slopes over 35 degrees where reactive and some could be remote triggered up to 10′ away. These slabs where F+ hard and about 35-40cm thick.