Old Man's Bowl - Small skier triggered micro-windslab/loose dry

AVALANCHE OBSERVATION
Old Man's Bowl

Drainage:

Submission Info
josh feinberg
Forecaster
Friday, March 29, 2019 - 5:00pm
Red Flags: 
Avalanche Type: 
Dry
Loose/Point-Release
Slope: 
40degrees
Trigger type: 
Skier
Crown Height: 
Less than 1 ft
Aspect: 
North
Weak Layer: 
Storm Snow
Avalanche Width: 
15ft.
Terrain: 
Above Treeline
Elevation: 
10 900ft.
Bed Surface: 
Old Snow
Avalanche Length: 
500ft.
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

Small skier triggered avalanche occured early afternoon today on the upper north facing slope of Old Man's Bowl on Mini Morrison (Mono-Jim).  I met the skier just as he was arriving to the parking lot and I was heading out.  Skier didn't realize he triggered it until a couple turns below when he saw over his shoulder the slough coming down, and he was able to turn wide right out of it's way.  I was able to go up and investigate, and found the trigger area to be about 10-15ft wide without a true crown.  The start of the slide was in an area of some shallow micro-windslab in the middle of the slope which the skier triggered, that slid down and began entraining loose snow and other areas of shallow softish windslab.  See attached photos, one of which shows an area of the jagged flank where ~1.5" thick windslab existed (this wasn't thick enough to propogate a fracture when I stomped around on it on the way up).  The slide ran ~500ft, extended to about 30ft wide at its widest point, and ran on a layer of hard very firm old snow (ski crampons were nice skinning next to the slide path).  The debris toward the bottom wasn't more than half a foot deep.  Just above the start of the slide in area of thicker windslab I dug some quick hand pits, which failed easily.  1finger+ 2-3" wind slab ontop of ~4" of first plus snow ontop of knife hard old surface (see attached video).  Stomping around in the area couldn't get anything else to move, as the slab here just didn't have the right combination of thickness and hardness. Much more of a loose dry slide, than a true wind slab avalanche.    

Avalanche Photos: 
Avalanche observation video: 
Blowing Snow: 
No
Cloud Cover: 
Clear
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Wind Direction: 
Southwest
Accumulation rate: 
None
More detailed information about the weather: 

Blue skies, mostly calm winds with occasional light SW gust.  Just below freezing temperature late afternoon at ~11,000.

Number of People Caught: 
0
37° 34' 1.7184" N, 118° 51' 5.0472" W
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