Series of storms to bring more rain to the Bay Area

As Northern California appears headed for an average rainfall season, the next in a series of storms is forecast to arrive Friday with rain in the Bay Area and snow in the Sierra Nevada.

The National Weather Service is projecting light rain to develop along the coast and in the North Bay on Friday morning before spreading inland during the afternoon.

Rainfall amounts are expected to range from about a half-inch to three-quarters of an inch in most cities, with lesser amounts in some inland valleys. San Francisco and the Peninsula could receive three-quarters of an inch, with the East Bay recording as much as two-thirds, and San Jose and the South Bay a half-inch, according to Drew Peterson, a meteorologist with the weather service. The Bay Area’s coastal mountain ranges and hills may receive up to 1.25 inches.

“It looks like just more beneficial rain,” Peterson said of the first storm. “We shouldn’t see flooding concerns with this one.”

Peterson said the second storm will “be coming in on the tail of that first one, dropping in right behind it, Sunday into Monday.” Snow levels in the Bay Area are forecast to lower late Sunday into Monday as a colder air mass impacts the region. The weather service said any lingering showers may produce snowfall in elevations above 3,000 feet Sunday night.

Meteorologists say there is the potential for a third storm in the middle of next week.

“The next couple weeks, the storm door will remain open,” Peterson said. “We’re in mid-winter type of pattern, with a series of systems keeping us cool and wet with maybe a day or two break inbetween systems.”

Cold overnight temperatures are expected again today before the next storm arrives. Recent storms have boosted the water picture in the Bay Area. Through Wednesday afternoon, San Francisco received 12.92 inches of rain since Oct. 1, or 91 percent of its historical average, while Oakland was at 10.06 inches or 86 percent, and San Jose’s total hit 8.38 inches or 96 percent.

The upcoming storm also means that travel to the Sierra Nevada will be difficult for the second weekend in a row, with several feet of new snow possible, according to the weather service. Snow levels are expected to be relatively low and passes could receive several feet of new snow.

A flurry of January and early February storms have boosted the statewide Sierra Nevada snowpack, the source of one-third of California’s water supply for farms and cities, to 125 percent of its historical average for this date on Tuesday, up from 69 percent on Jan. 1.

There are still about seven weeks before the end of the winter/snow season on April 1. The Sierra Nevada snowpack has measured at or above its seasonal average just once in the previous seven winters, including the drought years of 2012-2015, where the largest snowpack measured just 54 percent (in 2012).

On April 1, 2017 the snowpack measured 163 percent.

In 2016, the snowpack tallied 86 percent on April 1, and many Bay Area cities received 80 to 100 percent of their average rainfall totals. Most of the major reservoirs around the state continued to rise as billions of gallons of water poured in from rivers, streams and saturated hillsides, virtually guaranteeing that there won’t be mandatory summer water restrictions in most California cities this summer.

Shasta Lake, the state’s largest reservoir, has risen 36 feet since New Year’s Day, and on Tuesday was 66 percent full, or 97 percent of its historical average. Folsom Lake was 59 percent full, or 112 percent of its historical average for this time of year. And San Luis Reservoir, between Gilroy and Los Banos, was 87 percent full or 109 percent of its historical average.