End of below-average water year for North Coast marks start of new one, anticipated to be dry

A new water year began Friday, officially marking the end of a second-straight dry year for the North Bay, which saw a meager 39% of its historic average precipitation. And meteorologists expect another dry year as Sonoma County heads into what’s forecast to be another La Niña winter.

For the period that began Oct 1. last year and ended Thursday, Santa Rosa recorded 13.01 inches of rain. The region’s 30-year average is 36.28, according to Ryan Walbrun, meteorologist at the National Weather Service.

The water year is different from a calendar year because precipitation from the snow can’t be measured until it melts in the spring or summer.

San Francisco and San Jose, two other measurement bases for the Weather Service’s Monterey office, also recorded only 39% of their historic average, according to the agency.

The previous, with slightly better precipitation — 57% of the average for Santa Rosa — plunged the region and most of the state into a severe drought that doesn’t appear to be loosening its grip.

With another La Niña winter in store, Sonoma County can expect rainfall that is “marginal at best,” he said.

La Niña winters in Northern California are usually dryer than normal, while the Pacific Northwest will typically receive above-average precipitation, he said.

This is due to the Polar Jet Stream, which falls across Northern California dividing Washington, Oregon and the most northern counties of California from the rest of the state.

Santa Rosa has a good chance of rainfall starting Thursday and going through the weekend, with cooler temperatures countywide, Walbrun said.

“At least we have a chance on a little bit of rain next week,” Walbrun said.

You can reach Staff Writer Alana Minkler at 707-526-8511 or alana.minkler@pressdemocrat.com. On Twitter @alana_minkler.