The latest storm that moved through the area on Sunday was accompanied by periods of intense snowfall and moderate southwest winds. Precipitation rates of 1 to 2” per hour were recorded and sensitive wind and storm slabs developed throughout the period.
Precipitation Totals and Temperatures (as of 4:00 AM, 3/6/17)
Location Snow Water
VA Lakes (9445’) 13” 1”
Tioga Pass (9798’) 12” N/A
Ellery Lake (9645’) N/A .3”
June (9148’) 8” .3”
Gem Pass (10750’) N/A .6”
Mammoth Sesame (9014’) 10” .8”
Mammoth Pass (9,500’) N/A N/A
Rock Creek (9600’) 10” N/A
Saw Mill-Big Pine (10200’) 10” N/A
Big Pine Creek (10000’) N/A N/A
As the system exited the area on Monday and Tuesday, generally southwest winds remained blowing 15-40 mph at the top of Lincoln Mountain in Mammoth; gusts often hit 60 mph or more. Wind effects were reported from north of June down to Aspendell in Bishop. Mammoth Mountain Ski Patrol triggered wind slab avalanches with 3 foot crowns at mid mountain locations. Yesterday these wind slabs were still touchy, cracking around skis, on northerly slopes above 9000’. Though time will decrease your likelihood of triggering these wind slabs, shooting cracks and hollow sounding snow beneath your feet should set off alarm bells in your head.
Most recently, a warming trend has dominated the Sierra and it’s only going to get warmer through Friday. Wet snow instabilities have been seen on steep rocky slopes at lower and middle elevations. Sinking into wet, unsupportable snow and pinwheels rolling down the hill from rocky outcrops and from beneath your skis are some of the first signs that slopes are warming and becoming unstable.
At lower elevations where a melt-freeze crust remains below the snow surface, there is a buried weak layer that just might be triggered by larger point releases running down and overloading it. This layer of large faceted crystals has been seen near Rock Creek and in the June Lake area and is buried below the crust and about a foot of softer snow. Triggering this layer may be unlikely for now, but intense warming may change things over the next few days.