Pacific storm could cause power outages, flight delays and flooding Wednesday across San Diego County

The first of two back-to-back hits of rain will spread across San Diego County on Wednesday, producing pools of water on roadways, causing rivers to swell, and making Christmas Eve travel perilous, especially if rogue thunderstorms appear, the National Weather Service says.

A volatile Pacific weather system also could generate winds gusting 35 mph to 45 mph, potentially causing power outages, ripping up outdoor Christmas displays, and making some landings and take-offs at San Diego International Airport very rocky.

The airport was struck by 35 mph winds Tuesday morning when the leading edge of the storm started to move ashore. The system is drawing extra energy from moisture arriving from the subtropics.

The first wave of rain will drench the region from early Wednesday until late Wednesday evening, when it fades out. A second, smaller wave will arrive Thursday night and linger into Friday morning. Scattered showers could last into Saturday. And forecasters are eyeing the possibility that another storm will arrive at the end of the month.

The two waves of rain could collectively drop 2 to 3 inches of rain across the county — more moisture than many communities receive during the entire month of December. The precipitation will spread from the northwest to the southeast, with the heaviest rain expected near Oceanside and across inland valleys and the mountains.

San Diego lifeguards will have swiftwater rescue teams in place Wednesday and Thursday in North County, the San Diego River in Mission Valley, and near the border. The rain is expected to cause the San Diego River to rise to 7.2 feet, and for the Santa Margarita River near Fallbrook to reach 11.1 feet.

First responders are urging people to stay away from the river banks and to refrain from walking near the water’s edge of local beaches, where waves are projected to reach 5 to 8 feet, with periodic sets to 9 feet. Forecasters advise that people immediately seek shelter if they hear thunder.

Motorists are also urged to avoid driving through flooded roads.

It’s possible that the storm will produce a bit of snow late Thursday into Friday in the upper reaches of Mount Laguna and Palomar Mountain.