San Joaquin Mtn, Negatives - Avalanche Activity

AVALANCHE OBSERVATION
San Joaquin Mtn, Negatives

Drainage:

Submission Info
Forecaster
Saturday, March 17, 2018 - 2:45pm
Red Flags: 
Recent avalanche activity
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Obvious avalanche path
Avalanche Type: 
Dry
Slab
Trigger type: 
Natural
Aspect: 
Northeast
Terrain: 
Above Treeline
Bed Surface: 
Storm Snow
Number of similar avalanches: 
5-10
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

Noted extensive avalanching throughout the Negatives but not elsewhere along the ridge. It appears that portions of the Bowl that encompasses the Negatives failed independently, primarily N-NE aspects with a few exceptions. Many of the crowns were only barely visible, likely occurred early or mid cycle. Limited debris visible but most of the avalanches ranout onto the bench above the meadow at the bottom. Negative one failed early or mid cycle, the debris mostly stopped on the bench but a small ribbon continued to the valley floor. Many of the apparent crowns were below steep faces or cliffs and had significant southerly fetches. The largest avalanche D3(+?), R2 was directly under the cliffs on the south end of the Negatives ( ~6’ X ~400’ X ~1000’). My suspicion is the combination of heavy snowfall and wind loading was the prime contributor for most slides with the exception of the largest release, which likely failed at the graupel layer from 3/14.  The majority of the slides occurred on N-NE aspects, elevations 10000’ to 11000’. Given the recent avalanche activity, declined to do a crown profile until the avalanche hazard declines a bit more given the active wind loading during the day. This includes the normal approach route. A party of skiers who ventured up into the Negatives reported settlement at the Hourglass but no other activity. 

Avalanches:

Negatives

1, D3.5, R2 (NE Aspect, Elev. 10.600', Crwn Ht ~6', ~400’ X ~1000’)  

5+, D2, R1(N-NE aspects, Elev. 10,000' - 11,000', Storm Snow)

 

 

Avalanche Photos: 
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
None
More detailed information about the weather: 

Clearing skies after significant storm system. Cloud cover, scattered cumulous and cirrus. 

Number of People Caught: 
0
June Mtn.>Yost Lake > Hemlock Rdg 37° 44' 14.3772" N, 119° 5' 57.3504" W

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