The storm expected today might not leave Modesto soaking wet, but it could start to rebuild the snowpack that provides much of the region’s water.
The National Weather Service, in an update issued Wednesday, projected 0.19 inches of rain for the city through Friday. The forecasts look better to the east: 1.16 inches in Sonora, 1.47 in Strawberry and 1.08 in Groveland.
Snow forecasts range from 0 to 2 inches in the middle elevations of the Sierra Nevada to as much as 24 inches at the crest.
Much of that snow could later melt into the Stanislaus and Tuolumne rivers, the main water sources for much of the Northern San Joaquin Valley and Bay Area.
The rain, which was expected to arrive by Wednesday night, would be the first in Modesto since Dec. 7. That’s 53 straight dry days at a time that usually is the heart of the storm season.
The Modesto Irrigation District recorded 1.74 inches in its downtown rain gauge between the July 1 start of the rainfall year and Wednesday afternoon. The historical average through January is 6.65 inches. An average year is 12.19 inches.
The Weather Service warned that intense rain this week could stir up ash and other debris in the area burned by the massive Rim fire last year. Managers of Don Pedro Reservoir have booms in place to catch material that could be hazardous to boaters. A November storm raised the same concerns but did not result in any problems.
The central Sierra snowpack was 12 percent of average as of Tuesday, according to the California Department of Water Resources. The figure accounts for not just the depth of snow, but its density, which determines how much liquid water it will yield.
This is the third straight year of drought in California, and it looks to be the worst. Reservoirs that filled after the wet 2010 and 2011 are getting low. Mountain soil is drier than usual, meaning that some of the snowmelt will soak in rather than run off into reservoirs.
“While we can only hope for wet weather, we can act positively to conserve as much water as possible,” said Mark Cowin, director of the state agency, in a news release Wednesday. “Water conservation today is an absolute must.”