The most recent Atmospheric River moved out of the region Wednesday (2/22) with over two feet of new snow in favored areas (Mammoth and June Lakes). As the week progressed, Storm Slab instability declined as the snowpack settled and strengthened. The snowpack continues to settle in sheltered locations, with snow sensors showing continued settlement over the past 72 hours.
Moderate SW to W winds throughout most of the week redistributed the new snow onto leeward aspects (NW-N-NE-E-SE-S), primarily in the upper mid to upper elevations. Saturday, winds veered to the North resulting in significant snow transport (snow banners) over the high peaks from Whitney to Bishop with reports of natural Wind Slab avalanche activity. Sufficient time has elapsed that the Wind Slabs from earlier in the week have strengthened and bonded to the underlying snow. However, Sunday moderate/gusty SW winds developed mid-day forming new sensitive Wind Slabs on NW-N-NE-E-SE aspects in the mid to upper elevations, which have not had sufficient time to strengthen and bond to the underlying snow.
A weak storm system is forecasted to move thru the region Monday with up to 7” new low-density snow possible and moderate Southwesterly winds of 20-30 mph winds over the higher elevations. Forecasted moderate winds will easily redistribute the low-density snow onto leeward slopes, forming new sensitive Wind Slabs on NW-N-NE-E-SE-S aspects in the mid to upper elevations thru Monday. As a result, natural avalanches possible, human triggered avalanches are likely in mid to upper elevations primarily on NW-N-NE-E-SE-S aspects. Winds are forecasted to diminish by Monday night, which will allow Monday’s freshly formed Wind Slabs to begin strengthening and bonding to the underlying snowpack, reducing the Wind Slab threat by Tuesday. Natural avalanches will be unlikely, human- triggered avalanches will remain possible.
24 Hour Precipitation Totals and Temperatures (5:00 AM, 2/27/17)
Location Snow Water Current Temps
VA Lakes (9445’) N/A 0” 16.9
Tioga Pass (9798’) 2” N/A N/A
Ellery Lake (9645’) N/A 0 13
June (9148’) 1” N/A 14.9
Gem Pass (10750’) N/A .1” N/A
Mammoth Sesame St (9014’) 0 0 15.1
Mammoth Pass (9,500’) N/A N/A 18
Rock Creek (9600’) 0 N/A 14
Saw Mill-Big Pine (10200’) 0 N/A 11
Big Pine Creek (10000’) 0 N/A N/A