Winter rains not likely to ease California drought

Sunrise creates a shadow of a lone tree on the arid Lake San Antonio lakebed in Bradley, Calif., in September 2014. The once 16-mile lake in Monterey County now reaches less than five miles. Another dry year is leaving California's farmers in an ever-tighter bind, and the dairy industry is hit particularly hard. (Allen J. Schaben/Los Angeles Times/MCT) less Sunrise creates a shadow of a lone tree on the arid Lake San Antonio lakebed in Bradley, Calif., in September 2014. The once 16-mile lake in Monterey County now reaches less than five miles. Another dry year is ... more Photo: Allen J. Schaben / McClatchy-Tribune News Service Photo: Allen J. Schaben / McClatchy-Tribune News Service Image 1 of / 82 Caption Close Winter rains not likely to ease California drought 1 / 82 Back to Gallery

Drought conditions will likely ease in much of the West this winter, but not in most of California, according to a new climate report from the National Oceanic and Atmospheric Administration.

The report, released Thursday, indicates that conditions in the Pacific Ocean, which include a developing El Niño weather pattern, may prompt above-average rainfall for the southern third of California over the next three months.

The Bay Area, however, as well as most of the rest of the state, stands only a one-third chance of seeing above-average rain — and equal chances for below-average rain and a normal amount.

“There’s just not a strong enough climate signal to make a prediction,” said Mike Halpert, acting director of NOAA’s Climate Prediction Center.

The forecast bodes poorly for Northern California, where residents are hoping a wet winter erases some of the costs of the state’s driest three-year period on record, including tight drinking-water supplies, fallowed agricultural fields and damaging wildfires.

But even a wetter-than-average winter would provide only a modicum of drought relief.

“It will take significantly above-average precipitation to fill reservoirs and recharge groundwater,” Halpert said.

The only good news for California, according to federal climate experts, is that the stubborn ridge of high-pressure air that consistently formed off the coast in recent years, blocking storms from making shore, won’t be nearly as prevalent.

The probable El Niño, which forms when the jet stream reacts with warm ocean surface waters, will likely push enough moisture across the high sea to keep the ridge from settling in, Halpert said.

The absence of the ridge will also mean Pacific storms that were diverted to the Northeastern United States last year — bringing record snowfall to parts of the East Coast — aren’t as likely. In fact, New England is forecast for above-average temperatures this winter.

The El Niño, while likely to be weak, has a two-thirds chance of arriving by the end of the year, federal climate experts say.

The weather pattern could play a role in bringing more rain to Southern California, where climate experts project drought conditions to slowly subside. The drought is also expected to ease in the desert Southwest.

In most of California as well as Oregon and Washington, however, dry conditions will only intensify, according to the new report.

Kurtis Alexander is a San Francisco Chronicle staff writer. E-mail: kalexander@sfchronicle.com Twitter: @kurtisalexander