June Mtn.>Yost Lake > Hemlock Rdg. - New Snow Stability & Graupel

SNOWPACK OBSERVATION
June Mtn.>Yost Lake > Hemlock Rdg.
Submission Info
Forecaster
Saturday, March 17, 2018 - 2:45pm
June Mtn.>Yost Lake > Hemlock Rdg
Snowpit Observations
More detailed information about the snowpack: 

 

Observer: d lewis
Loc: Hemlock Ridge
Lat/Lon:37.7431, -119.1022
Elevation: 10000 f
Aspect: NNE Angle: 37°
Signs of Instability: Recent Avalanches, Whoomphing, Wind Loading
Sky Cover: BKN
Precipitation: No Precipitation, Very light snowfall < .5 cm/hour
Wind Speed: Calm
Wind Direction: N
Current Temp:-5 to -10°C Trend:➚
Blowing Snow: Moderate
New Snow 24-Hours:50cm Storm:50cm 
Boot Penetration: 45cm
Snow Stability: Good
Stability on similar slopes:Good
Avalanche Danger: Considerable trending toward Modrate. 4 Stability Tests: CT17 Q3 41cm CT14 Q3 41cm Very poor failure. Partial collapse/ crumble CT27 Q2 27cm Failed 1 of 3 ECTN27 Q2 27cm. 

Toured over to Hemlock Ridge at the north end of San Joaquin Mountain from June Mountain to assess the new snow stability and look for the graupel layer noted on Dream Pk 3/14. 30 + cm.  12” to 18” of new snow in the trees west of the ski area on descent to Yost Lake, some settlement cones and cracks noted, which indicates the snow has settled considerably and is strengthening. Areas receiving direct sun beginning to moisten at the surface and forming a light melt/freeze crust at the surface as the snow cools. The meadow and Yost Lake snow surface was lightly wind scalloped with obvious drifting from the SW prior. 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. No avalanche activity noted further north along the San Joaquin. Ascended to the top of Hemlock Ridge, hand shears moderate to hard and not very planer. Snowpit at 10000’ showed mixed results. Graupel was evident but not nearly as reactive. All test were mixed with irregular results. Ski cuts produced some sluffing on steep shelter terrain but didn’t run far, unlike the day previous. As you descend below 9000’ snowpack is thinner with more objective hazards (downed trees, rocks, stumps, etc.)

Additional avalanches noted on Mt. Wood as described by previous poster. Most debris fields stopped half way down the alluvial apron. Noted multiple debris fields at the base of Carson Pk’s steep rocky North Face with significant debris piles in the Devil’s Slide. Also saw four small Wind Slab avalanches on Wilson Butte, near 395.   

Snowpit or crown profile photo or graph: 
Snowpack photos: 
Negatives 1 Crown Lines
Negatives 2 Crown Lines
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
None
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
More detailed information about the weather: 

Cloud cover a mix of mid-level cumulous and scattered cirrus. Calm winds until you reached ridgeline where winds were light but noted moderate windloading further east along the flanks of Carson Pk. 

ESAC receives support from ...