The Mono Basin’s wet weather suddenly ended January 3rd, and aside from 0.16 inches of precipitation on January 30th, there was no measurable precipitation until February 16th! That is 27 dry days in a row, then one day of precipitation, followed by another 16 dry days! Total January precipitation in Lee Vining added up to 0.73 inches of water in 10.9 inches of snow. You can see our Internet weather rain gauge results (slightly less) here, as well as our recent official NOAA weather submissions here.
A characteristic of California’s winter weather is this mid-winter dry spell that allows us to put down our snow shovels and catch up on our sun. There is an excellent discussion of its impact on San Francisco rainfall by Jan Null here. Null relates that for San Francisco, El Niño years have an average of 17 dry days and La Niña years have an average of 21 dry days, with a minimum of 8 and a maximum of 42. If we use this as a measure of comparison for the Mono Basin, this year’s mid-winter dry spell was very much on the lengthy side of things.
Despite the dry weather, Mono Lake rose about a tenth of a foot in January to 6382.0 feet above sea level. February 1st snow surveys found 140% of average snowpack (88% of the April 1st average). By this week, the snowpack in the Eastern Sierra has reached the April 1st seasonal average essentially everywhere, including in the Mono Basin. The February 1st preliminary runoff forecast for the April 2011 to March 2012 runoff year is 111% of average for the Mono Basin and 124% for the Owens Valley.
The February storms that finally ended the dry spell dropped 21 inches of snow (above average for February) containing about 1.81 inches of water. More storms are expected at the end of this week, and if they drop about an inch of precipitation, February will reach the average mark for precipitation in Lee Vining.