Big, slow, long-lasting storm could drop 1 to 3 inches of rain at coast this week and produce lightning and powerful waves

San Diego County’s coast and inland valleys could receive 1 to 3 inches of rain from a large, slow, disjointed storm system that’s expected to last from early Tuesday to late Friday, ending the region’s dry spell just before Christmas Eve, the National Weather Service said.

The abrupt change in weather could cause widespread flash flooding in urban and rural areas and generate lightning west of the mountains, which is comparatively rare. Pollution will flow into creeks and local coastal waters.

Conditions will be worse in Orange and Los Angeles counties, the weather service said.

The first phase of the storm will arrive late Monday or early Tuesday, producing sporadic showers in most of the county. The mountains should get about 0.25 inches of precipitation while the rest of the region receives about 0.20 inches. There’s also a chance of lightning starting late Tuesday.

The core of the storm, which originated in the Gulf of Alaska, will drop into Southern California on Wednesday and produce on-and-off rain into Friday or Saturday. The storm, which will peak Wednesday into Thursday, will draw extra moisture from the subtropics.

It also will pick up unstable air, which could translate into thunderstorms through late Friday. Winds will gust hard out of the south and could make driving tricky, at times, along Interstate 5 and Interstate 8.

Forecasters say the coast will get drenched with as much as 2.25 inches of rain, with the heaviest precipitation falling north of downtown San Diego.

“We could reach our seasonal rainfall average with these storms,” said Casey Oswant, a weather service forecaster.

Since the rainy season began on Oct. 1, San Diego International Airport has recorded 0.62 inches of precipitation, which is 1.45 inches below average. Ramona as received 1.07 inches, which is 1.62 inches below average. And Oceanside has gotten 1.61 inches, which is 0.74 inches below average.

San Diego averages 9.79 inches of precipitation during the rainy season, which lasts from Oct. 1 to Sept. 30.

The storms will be warmer than normal, which means that there won’t be any significant snow in the mountains.