Powerful Pacific storm will reach San Diego County about 4 p.m. Thursday

It’s not going to be a white Christmas in San Diego County, but it will certainly be a wet one.

The tail of a Pacific storm that will drop 6 to 8 feet of snow in the Sierra Nevada will move ashore in San Diego about 4 p.m. on Thursday and unload 1.5 to 2.25 inches of rain at and near the coast by early Friday, says the National Weather Service.

The storm, which is drawing lots of moisture from the subtropics, also could deliver 2.5 inches of rain across inland foothills and valleys, as well as 3 to 4 inches in Julian and up to 5 inches on Palomar Mountain.

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The system will blow into North County first then spread east and south. Gusts could reach 20 to 25 mph from Oceanside to Imperial Beach.

A flash flood watch will be in effect from 7 p.m. Thursday to noon on Friday, and wind advisories may be coming. Winds are expected to gust 20 mph to 25 mph, which could buffet commercial jets taking off and landing at San Diego International Airport.

The airport estimates that it will handle about 1 million commercial jet passengers between Dec. 17 and Jan. 3, a roughly 25 percent increase over the same period a year ago. Air traffic is expected to be especially busy on Thursday.

Driving also could turn into an adventure, especially before dawn Friday. That’s when some of the heaviest precipitation will fall. Forecasters say Oceanside and Carlsbad could get 2 to 2.25 inches or more of rain before the first wave of the storm passes, while San Diego ends up with roughly 1.8 inches, or more.

“Christmas is going to feel more like winter than usual,” said Stefani Sullivan, a weather service forecaster.

A second round of rain is expected to begin late Friday or early Saturday and last into Sunday. It’ll mostly be in the form of periodic showers. But San Diego could pick up an additional 0.25 to 0.50 inches of rain over the weekend. And it’s going to be cold. Saturday’s daytime highs will only reach the mid-to-upper 50s along the coast. Communities like Julian will barely make it into the low 40s, and overnight lows will be near freezing.

The region will experience prolonged rain because the storm, which originated in the North Pacific, is drawing lots of moisture from an area east of Hawaii. It is generating an atmospheric river that will affect the entire state, especially the Sierra, where the air will be cold enough to convert the rain to heavy snow.

Forecasters say this system, and the one California got a week ago, will put a dent in the state’s drought. But many more sizable storms will be needed to significantly replenish reservoirs.