If you’re able to work from home Thursday, you should. Friday, too.
The polar jet stream is plunging south and will extend from the South China Sea to San Diego, creating a conveyor belt of moisture that will produce 1.5 to 2 inches of rain near the coast and across inland valleys, and 2 to 6 inches in the mountains, the National Weather Service said. The storm also is pulling moisture from east of Hawaii, supercharging the storm.
A flood watch will be in effect across the entire county from 6 a.m. Thursday to 10 a.m. Friday. The storm system could do everything from create freeway gridlock to trigger mudslides to knock down power lines.
The weather service said Wednesday afternoon that the county could get 1 to 3 inches from the next storm, which will arrive late Sunday or early Monday.
Here’s a closer look at what’s likely to happen, and when, on Thursday and Friday.
First up: wild winds
The storm will begin with powerful winds out of the south lashing the county’s entire coastline, roughly from 1 a.m. Thursday to early afternoon. Expect 35 to 45 mph gusts, and possibly a few as high as 50 mph.
Forecasters say cross-winds will likely force San Diego International Airport to suspend flight operations for part of the morning. (Check for flight updates at san.org.) The winds also could snap tree branches and upend loosely-rooted trees, notably in Imperial Beach, Torrey Pines, La Jolla Shores and Del Mar.
Heavy rain will follow
Light rain is expected to fall from roughly 6 a.m. to 9 a.m. Thursday, followed by heavy rain through 3 p.m., then moderate rain until about 6 p.m. The rain will then taper off. But a second round of rain will likely come Friday morning.
Here is total projected rainfall for 14 communities. These numbers represent average expected precipitation, but some areas could get much higher rainfall — possibly up to 3 inches:
Palomar Mountain: 2.45 inches
Mount Laguna: 2.11 inches
Julian: 1.97 inches
Oceanside: 1.74 inches
Miramar: 1.62 inches
Fallbrook: 1.60 inches
La Mesa: 1.49 inches
El Cajon: 1.44 inches
Rancho Bernardo: 1.42 inches
San Diego International Airport: 1.38 inches
Chula Vista: 1.37 inches
Campo: 1.35
San Ysidro: 1.25 inches
Borrego Springs: 0.48 inches
Rivers will swell
The San Diego River in Fashion Valley will reach monitor stage of 7-feet 5-inches by 2 p.m. Thursday and the 10-foot flood stage by 6 p.m. The water will increase to 10-feet 1-inch late Thursday night.
The Santa Margarita River at Camp Pendleton will rise to 9 feet, 6 inches by Thursday night. There’s only a small chance that the river will reach the flood stage of 11 feet, 2 inches by early Friday.
The San Diego Fire Department’s lifeguard division will have swiftwater rescue teams in areas that commonly flood during big storms.
If swiftwater rescues are needed, the public should dial 9-1-1.
Urban flooding is likely
Forecasters say that rainwater from that powerful storm that hit the region on Jan. 22 is still trickling downward in the soil in many areas, making the region more susceptible to flash floods as well as rock and mudslides later this week.
The threat also is high because the coming storm could dump 0.75 to 1 inch of rain per hour in some areas. And it’s possible that thunderstorms will erupt west of the mountains on Thursday night, which would further intensify rainfall.
“The areas that flooded in south San Diego on Jan. 22 could have real problems if the rain comes down real heavy,” said Liz Adams, a weather service forecaster. “Places like Coronado, National City and Encanto.”
The public is being urged to activate the wireless emergency alert feature on their cell phones to get advance notice of trouble spots and to sign up for alerts at alertsandiego.org.
People should stay away from coastal bluffs, especially at Torrey Pines State Reserve, Del Mar and Beacon’s Beach in Encinitas, where there is a lot of loose soil.
A high surf advisory will be in effect from 2 a.m. Thursday to 6 a.m. on Saturday. Waves will range from 5 to 7 feet, with occasional sets of 8 to 10 feet, and could cause serious erosion in many areas. West-facing beaches will get hit hardest.
Expect a nightmare commute
The storm could cause water to pond on local freeways, slowing traffic and making driving riskier, forecasters say. That has proven to be a particular problem on parts of state Route 78 in North County. Ponding also could occur on Interstate 15 near the Carmel Mountain Road exit. Commuters can track freeway accidents at cad.chp.ca.gov.
The storm also poses a problem for trolley riders, since many stations offer little or no shelter from storms. Live alerts are available at sdmts.com.
U.S.-Mexico border crossing times also could grow at San Ysidro. Get updates on wait times at bwt.cbp.gov.
Did El Niño create this storm?
We got an answer from Shang-Ping Xie, a climate scientist at UC San Diego’s Scripps Institution for Oceanography.
He said that El Niño does not produce specific storms, it but can influence the movement of storm tracks — which in turn can contribute to the sort of heavy rain that fell at San Diego International Airport on Jan. 22.
Staff writer Blake Nelson contributed to this report.
