Mini Morrison - Up Old Man's Bowl, down NW gully

Posted March 8th, 2010 by joshf

Location

United States
37° 34' 7.1904" N, 118° 51' 8.5392" W
Date and time of observation: 
March 8, 2010 - 1:30pm
Region: 
Convict Lake Area
Observation Type: 
Snowpack
Route: 

From convict lake parking, up to tobacco flat, up Old Man's Bowl, down NW gully, down to lake.

Red Flags: 
Recent loading by new snow, wind, or rain
Weather Observations
Blowing Snow: 
Yes
Wind Speed: 
Moderate
Wind Direction: 
East
Air temperature: 
Below Freezing
Air temperature trend: 
Cooling
Cloud Cover: 
100% of the sky covered by clouds
Precipitation: 
Snow
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Left car with partly sunny skies, warm.  About an hour later winds picked up a good deal, temps dropped, and snow started falling (light with short periods of moderate)

Snowpack & Snowpit Observations
Information about the snowpack/snowpit: 

Evidence of some small wet rollerball activity on east facing slope that occured yesteday (originating just below rock bands).

Test pit dug 10,700' (100 feet below ridge) on East-North-East facing aspect of Old Man's Bowl.  Small amount of recent wind
deposited snow.  Skin track blowing in fairly quickly. 
Total snow depth = 200cm
200-180=fist
180-165=4finger
165-135=1finger
135-134=knife hard crust
134-128=4finger weak layer larger grained with facets       CT29Q1.5 - failed in top portion of this weak layer.
128-124=impenatratable very hard crust
124-110=pencil  (only dug pit down to 110cm)

Skied NW facing gully from top of old man's bowl.  Scattered small pockets of sensitive recent wind slab (3 inch depth)
that would fracture and slide ~5 feet on small convexities. 
At very bottom of run at lake level on small (10' tall) steep convexity at edge of small aspen grove, Small failure triggered
with 6-8" crown, 15 feet wide.  Very recent wind load. 

 

Comments: 

Winds picked up a good deal during tour, (swirling, but predominantly from the east in this area) and light snow began falling with short periods of moderate intensity.  Some sensitive wind-slabs began forming and wide range of elevations all the way down to convict lake level.  These wind slabs will quickly become more and more of an increasing concern as the winds continue, especially since there is loose snow available for transport.  These are the kinds of conditions that have led to serious avalanche accidents in the sierras in the past that have resulted in fatalaties.  Be careful out there! 

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