SAN DIEGO -
A cold low pressure system from the Gulf of Alaska moved southward toward San Diego County Tuesday, forecasters said.
The system should arrive in San Diego County late Thursday and linger through early Saturday, according to the National Weather Service.
It is expected to bring much cooler temperatures to the region. The Weather Service forecast highs for Friday in the 50s and 60s at lower elevations and in the 30s and 40s higher in the mountains.
"These temperatures will be 25 to 35 degrees cooler than high temperatures early this week," according to the agency.
The Weather Service also forecast the system could drop one-tenth to a quarter-inch of rainfall near the coast to around a half-inch in the mountains. Less than a tenth of an inch of rain is expected in the deserts.
The snow level is expected to lower to 4,000 to 4,500 feet Friday afternoon and 3,000 to 3,500 feet Friday night through early Saturday, with a few inches of snowfall possible above 4,000 feet and around a half-foot of snow on the highest peaks.
Mountain and desert residents also can expect west winds to gust around 50 miles per hour late Thursday through Friday night.
"This weather could be deadly for unprepared campers or hikers," according to the Weather Service.
Fog advisory in effect until 8 a.m.
A shallow marine layer and weak coastal eddy brought dense fog to parts of San Diego County early Tuesday, reducing visibility to less than a quarter of a mile in some places.
The National Weather Service issued a dense fog advisory effective until 8 a.m. for areas extending from the beach to around Interstate 5. The greatest stretch of fog goes from La Jolla to the Mexican border, according to an NWS advisory.