On November 12th, 2009, at approximately 5:30 pm, the roar of hail on metal roofs resounded throughout the town of Lee Vining. It hailed really hard for about an hour, followed by a transition from 1/4 inch hail to smaller and smaller hail until it turned to snow by 8:00 pm. The snow continued until around 9pm. The next morning we measured about 0.56 inches of water. About 0.75 inches of ice pellets was covered by 1.5 inches of snow.
This is likely an overestimate, since I watched the hail bounce off the roof of a building into the rain gauge, which sits about 7 feet away from the edge of the roof and about 7 feet lower. Most of the bouncing hail fell short of the rain gauge (and onto the snow board where we measure snow/ice), but during the most intense downpours more hail bounced off the roof as far as the rain gauge.
It is hard to say how much of an overestimate our measurements are, since the storm was very localized (Mono City and June Lake got much less snow), and Yosemite Valley recorded about 1/2 inch of precipitation–the highest of any automated rain gauge in the California/Nevada River Forecast Center’s list of automated gauges.
Our automated rain gauge that sends data to our Website every 15 minutes was also not functioning–the next day I found a pine needle that had fallen into it and caused the tipping bucket to remain weighted to one side. After cleaning it out, I tested it by scraping snow/hail off the ground over a similar area as the gauge opening and putting it into the gauge. The heater melted it and the gauge reported a volume of water–0.68″–that was similar to what fell last night, but in no way precise.
The NASA photo below shows the white snow-covered part of the Mono Basin lies to the southwest of Mono Lake.