Probability of Rain Today Put at 100%

Heavy rain will begin falling this afternoon, taper off a bit on Saturday and then resume in earnest Sunday, continuing into next week and bringing a strong likelihood of renewed mudslides and flooding in the Southland, forecasters said Thursday.

Dean Jones, a meteorologist with WeatherData Inc., which provides weather information for The Times, said the coming storms are being directed here by a shift in the jet stream--the same southward shift that propelled warm, moist tropical air into Southern California earlier this month, triggering destructive floods and landslides.

The National Weather Service--in a prediction unusual, if not unprecedented, for its lack of hedging--said there is a 100% probability of rain in the Los Angeles area this afternoon.

As much as two inches of rain could fall in the foothill communities surrounding the Los Angeles Basin this afternoon, with perhaps twice that much on the lower mountain slopes. The National Weather Service said most of the precipitation above 5,000 feet should fall as snow, with a foot or more expected at mountain resort levels.

Jones said that after a break on Saturday night and Sunday morning, an “even bigger” storm should strike Southern California Sunday night or early Monday.

“That one will bring two to four inches of rain to Los Angeles, and even more in the foothills and mountains,” he said. “With the ground already saturated, that one will definitely bring some more flooding and mudslides. Very definitely.”

Jones said that, as they did earlier this month, the high altitude winds of the jet stream have swung south over the central Pacific Ocean and have begun to split into two arms, with the southern arm headed right for Southern California. As the tropical moisture carried by the southern arm collides with the mountain ranges of Southern California late this morning, he said, it will be deflected upward in a phenomenon known as “orographic lift,” condensing as it cools and then falling as heavy rainfall. “The rain will start falling at about noon,” he said. “The areas hardest hit will probably be in Ventura County and in the San Gabriel Valley. There’s the potential for some pretty heavy rains.”

The rain is expected to taper off to showers tonight and Saturday morning, with variable clouds Saturday night and Sunday morning.

“Then, by late Sunday or early Monday, the next storm--the big one still sitting north of Hawaii on Thursday--will make landfall in Southern California,” Jones said. “It’ll be there in time for the Monday morning rush hour.”

Jones said the rain will probably continue, off and on, through Wednesday.

The Los Angeles Civic Center rainfall total for the season--which runs from July 1 through June 30--stood at 11.76 inches on Thursday. That compares to a normal season’s total for the date of 6.60 inches. Last year’s total for the date was 1.60 inches.

On Thursday, with telephone service still disrupted to more than 55,000 Southern California customers because of damage caused by the earlier flooding, officials for Pacific Bell and GTE said it probably will be two weeks before all the phones are working properly. And that’s assuming there isn’t any more flood damage.

David Dickstein, a spokesman for Pac Bell, said most of the damage occurred at individual businesses “when things that don’t usually get wet, got wet.”

“The equipment down here isn’t designed for that kind of weather,” he said.

Dickstein said that most of the problems have left affected customers without service, but some involve “scratchy” noises on the line and similar inconveniences.

He and Mike Murray, a spokesman for GTE, said company repair crews, supplemented by outside contractors, are working around the clock to restore full service.