January has been unusually sunny across the Bay Area, but a shift in the weather is expected Saturday and Sunday. The return of the marine layer will bring increased cloud cover and lower temperatures, with highs struggling to reach 60 degrees in most areas.
However, the weekend forecast remains unclear due to uncertainty of the position and strength of an upper-level low-pressure system off the California coast. This uncertainty has implications for both the Bay Area’s weather and the Santa Ana wind forecast in Southern California.
• Fog tracker : San Francisco and Bay Area weather and visibility map
Low clouds, fog and cool temperatures
The haze and low clouds spreading across the region Friday morning signal a shift to more easterly, onshore winds. This wind pattern creates a shallow surface inversion, trapping moisture and generating low clouds and fog…