Wet Week Expected as Two Storms Approach : Weather: The first powerful front is due late tonight, the second may arrive Thursday. Prolonged heavy rain could cause flooding, officials say.

The first of two Pacific storms is expected to roll into Southern California tonight, initiating several days of heavy rain and raising the possibility of flooding by the end of the week.

The National Weather Service has issued a storm watch calling for high winds and nearly a foot of snow above 6,000 feet in the San Bernardino Mountains by Saturday.

The first storm is expected to hit late tonight and continue to pound the area with heavy rains until Wednesday, when forecasters expect a break in the downpour. On Thursday, the second storm is expected to move in and drench the Southland for at least two days.

The two storms are being fueled by tropical jet streams south of Hawaii.

Forecasters expect up to four inches of rain in the Los Angeles Basin, as much as five inches along the coast and about seven inches in the mountain areas before the pair of storms move east, leaving clear skies on Saturday.

“It looks like another stormy week, where there could be the renewal of flooding problems in Southern California,” said Marty McKewon, forecaster with WeatherData Inc., which provides weather information to The Times.

“We’ve had a lot of rain and the ground basically is pretty saturated,” he said. “As it starts to get more heavy rain, a lot of it will run off and lead to flooding.”

By the end of the week, McKewon said, the storms could create conditions ripe for mudslides, especially in the mountains.

On Sunday evening, a brief but vigorous storm hit the Southland, with hailstones falling from Altadena to San Juan Capistrano. Scattered power outages from Norco to San Clemente were reported during the furious storm, which was accompanied by thunderstorms and lightning.

In Agoura Hills, a three-bedroom house and pool on Via Amistosa was sliding downhill as a result of Sunday’s downpour.

By late Monday, the house had moved nine inches. City geologists and other experts determined that the hillside apparently was undermined by rainwater soaking the soil, according to authorities at the scene.

Owner Richard O’Linn spent the day removing valuables with help from friends to comply with an Agoura Hills city order forcing him to vacate the potentially unsafe structure.

Lt. Jim Glazar of the Lost Hills Sheriff’s Station said several other homeowners in the community just south of the Ventura County border have been warned that their homes could suffer some movement as well.

The storm produced rainfall ranging from 0.02 inches in the San Bernardino area to 0.76 inches near Mt. Wilson.

So far this season, Los Angeles has registered 19.82 inches of rainfall, more than double the normal amount.