Rain Expected, but It Won’t End Drought : Weather: The high-pressure system that deflected storms to the north yielded a bit. Chance of rain today in San Diego put at 60%; 80% on Thursday.

California’s “storm door,” mostly barred for months by persistent high pressure over the Southwest, cracked open a bit Tuesday, admitting a welcome weather system expected to produce three or four rainstorms through the weekend.

If the forecasters are right, it should be raining today in many parts of Southern California, with half an inch to an inch of precipitation in coastal regions and 2 to 3 inches in the mountains, with snow at high elevations.

“Rain coming. . . . We hope,” the National Weather Service said in a special weather statement issued Tuesday.

Light rain was expected to move onshore in Santa Barbara County on Tuesday night, then spread over Southern California coastal plains and mountains today, with a chance of showers in the deserts.

Residents from Central to Northern California as far as Eureka on the coast north of San Francisco were also told to expect rain, with snow in the Sierra Nevada above 8,000 feet, lowering to 6,000 feet as colder air moves in later in the week.

But, the weather service’s statement offered more than prospects of a single rainstorm:

“Of greater importance in making a dent in the drought . . . the upper air pattern shows signs of opening up the storm track across the eastern Pacific, allowing a series of storms to strike this area during the next several days.”

Meteorologist Steve Burback of WeatherData Inc., which provides forecasts for The Times, expected “at least two or three other storms” to come with the storm track and into the state during the rest of the week.

Burback said the storm waves were moving straight at California, instead of being blocked to the north by the long-lived high-pressure system that has persisted in the Southwest.

In San Diego, “we have a 60% chance of rain this afternoon, which will increase to 80% tonight and Thursday,” said Wilbur Shigehara, forecaster for the National Weather Service in San Diego.

A third storm northwest of the Hawaiian Islands may arrive by Friday, but it is the weaker storm of the three, he said.

But, before it’s all over, San Diego could receive half an inch of rain and more in the mountains.

“It won’t be a drought-breaker, but it’ll help,” Shigehara said. “At least we won’t have to water the lawn.”

The storms will also bring gusts up to 25 m.p.h. and surf of 4 to 6 feet through Thursday. Daytime temperatures will hover in the 60s.

The storms will bring the first significant rains since January, he said. The last major rain was Jan. 9 when a little more than a quarter of an inch fell.

San Diego is 4.20 inches below normal rainfall for the season, which runs from July 1 through June 30, Shigehara said. So far this season, San Diego has received 2.34 inches, contrasted with a norm of 6.54 inches.

The brief stormy period will give way to a drying trend over the weekend after a weak high pressure returns, he said. Cloudy skies and a few sprinkles are are expected on the weekend.

Drought specialist Dean Thompson of the state Department of Water Resources greeted wet-weather predictions as the “most encouraging news we’ve had in almost a month.”

“It’s somewhat similar to the way we started February,” Thompson said. “We started with the storm door open. We had storms on Feb. 2 and 4 and were expecting more to come, but the third storm broke up and headed north, and that was the end.”

The earth is so parched that there is very little runoff, he said.

“It’s welcome if it even showers,” Thompson added. “But to do any good, we need the first one to get things wet and get the others to start stream flow. And we need a lot more after that to have any impact.”

The National Weather Service joined in Thompson’s hope.

“We are so far below normal rainfall that it will take a series of heavy storms over a three- to four-week period to dent the record dry spell that California is experiencing,” the agency’s statement said.