A slow-moving storm that caused widespread flooding Thursday in Ventura County will reach San Diego by midnight and drench the region through Friday, and also could spark lots of lightning, the National Weather Service said.
Large rain cells moved in Los Angeles County and were expected to spread south into Orange County before the tail of the storm arrives in the San Diego area.
Locally, the system is expected to drop 1.00 to 1.50 inches of rain from the coast to inland valleys and foothills by late Friday. The heaviest precipitation is expected to fall in the northern part of the county, from Oceanside and Carlsbad off to Palomar Mountain in the east.
The region also will get hit by stiff winds out of the south that could break or topple the county’s ubiquitous eucalyptus trees, which become loose in saturated soil. The winds will arrive late Thursday and last into Friday, gusting upwards of 30 mph in some areas as the system peaks.
It is possible that the lower San Diego River will reach flood stage by dawn on Friday. Even if it doesn’t, there’s likely to be enough rain to affect the flow of traffic to the Fashion Valley Mall in Mission Valley in the midst of peak last-minute Christmas shopping.
In San Clemente in southern Orange County, the city shored up the Casa Romantica site of a hillside slide that threatens the railroad tracks of the coastal rail line that links San Diego to Los Angeles.
“The hillside has been tarped with visqueen in preparation for the stormy weather expected in the next few days,” said City Manager Andy Hall.
A flash flood watch will be in effect for all of San Diego County until 10 p.m. The city of San Diego will provide residents up to 10 empty sand bags at 11 recreation centers; locations are available online at sandiego.gov.
Forecasters also say the storm could produce lightning west of the mountains, mostly because the system — a classic cut-off low — is drawing unstable air from a region hundreds of miles off the west coast of Baja California. Lightning rarely occurs at the coast.
The weather service stopped short of calling this an El Niño storm. But forecaster Alex Tardy said El Niño is starting to affect the path of the northern jet stream, which can in some cases steer storms and damaging waves into Southern California. Heavy surf was already rolling ashore along the entire San Diego County coastline by Tuesday afternoon.
The storm is fairly warm, which will limit its ability to generate snow in the mountains. But it is possible that a modest amount of very wet snow will fall on Palomar Mountain and Mount Laguna on Friday.
The weather service stressed that lightning is possible across highly populated areas. The agency’s parent, NOAA, offered the following advice for staying safe:
— If you are outside and you hear thunder or see lightning, immediately seek shelter. Seek out a sturdy building, and stay away from electrical appliances and plumbing fixtures. If possible, stay inside an interior room.
— If you are inside a vehicle, roll the windows up and avoid contact with any conducting paths leading to the outside of the vehicle, such as radios, CBs, ignition, etc.
— Not all types of buildings or vehicles are safe during thunderstorms. Unsafe buildings include those that have exposed openings, such as beach shacks, metal sheds, picnic shelters or pavilions, carports and baseball dugouts. Porches are dangerous as well.
— Convertibles offer no safety from lightning, even if the top is up. Neither do vehicles with open cabs, such as golf carts, tractors and construction equipment.
— Lightning can travel great distances through power lines, especially in rural areas. Do not use electrical appliances, especially corded telephones, unless it is an emergency. Cell phones are safe to use, as are laptops that are not plugged in.
— Do not take a shower or bath during a lightning storm, as both water and metal are good conductors of electricity.
Union-Tribune reporter Phil Diehl contributed to this story.
