A weak short wave moved through the region Thursday depositing about 2” of snow with strong SW winds, which quickly forming localized sensitive Wind Slabs on NW-N-NE-E-SE aspects. Late Thursday into Friday, heavy snow began falling as another Atmospheric River streamed into the region. Freezing level hovered around 7000’ with 12” to 30” of new snow reported with light winds, which limited Wind Slab formation to isolated exposed mid to upper elevation locations. Friday as the storm began to move off to the east, widespread tender Storm Slabs and sloughing were observed, especially in the June / Mammoth region were snowfall was the heaviest. This was confined to soft slab instability within the new snow. There were many reports of extensive soft storm slab releases and sloughing in steeper mid to low elevations Friday around the Mammoth and June area, as well as from Ice Climbers in Lee Vining Canyon with avalanches burying the ice climbing approach boot pack Thursday and Friday. Skies cleared Saturday with light Southwesterly to Westerly winds, as the day progressed, winds began to picking-up Saturday afternoon forming Wind Slabs on NW-N-NE-E-SE-S aspects primarily in exposed mid to upper elevation terrain along ridgetops, crossloaded gullies and depressions, and near and around terrain features that promote drifting and loading. As the skies cleared Saturday, temperatures began to climb under the mid-February sun with extensive Loose Wet releases observed throughout the region on all solar aspects, especially around rock outcrops and below cliff bands on steep slopes. Some observed Loose Wet releases were quite large and could have easily buried person, especially if a terrain trap was involved. Saturday’s mild conditions has helped to the snowpack to settle and strengthen, decreasing the Storm Slab potential through Sunday.
Storm Totals and Hi Temperatures (2/17 -2/18)
Location Storm Snow Storm Water Temps
VA Lakes (9445’) N/A 0.5-0.7” 34.2
Tioga Pass (9798’) 12” N/A N/A
Ellery Lake (9645’) N/A 0.6” 34
June (9148’) 20” 1.9” 36.3
Gem Pass (10750’) N/A 1.2” N/A
Mammoth Sesame St (9014’) 25” 2.1” 32.7
Mammoth Pass (9,500’) N/A N/A 36
Rock Creek (9600’) 7” N/A 33
Saw Mill-Big Pine (10200’) 10” N/A 31
Big Pine Creek (10000’) 16” N/A N/A