Dense sun-choking fog, the likes of which we’ve rarely seen in the Valley during and since the drought, returned in full force Monday, prompting the National Weather Service to issue a fog advisory and “high transportation risk” in fog-bound areas.

The National Weather Service posted an “experimental fog severity index” on its website that’s pretty much a travel advisory, said Jim Bagnall, a meteorologist with the National Weather Service in Hanford. “It’s kind of a new messaging format,” he said. “It’s basically a dense fog advisory.”

Driving conditions could be hazardous with visibility down to a few hundred feet, so drivers are cautioned to slow their speeds and watch for stopped vehicles.

Conditions will be similar on Tuesday morning, with more dense fog gripping the Valley.

AT 11:50 AM…satellite loop shows widespread low clouds and fog beneath the passing higher clouds, shown here in purple and blue. Drivers should remain alert for areas of fog with visibilities between 1/2 and 1/4 mile. #CAwx pic.twitter.com/JogwGlTc6E

— NWS Hanford (@NWSHanford) January 15, 2024

Rain and Snow Coming

A high-pressure system parked over Central California that’s holding the fog bank in place will get a nudge Tuesday night with the tail-end of a low-pressure system that will bring “meager” rain to the Valley and snow to the Sierra. Less than a tenth of an inch of rain is forecast for Fresno by the time it ends on Wednesday, Bagnall said.

Temperatures will be warmer than normal, with Fresno’s forecast high of 60 on Tuesday and 61 on Wednesday, and about 10 degrees higher than normal through the end of the week, he said.

But more substantial amounts of rain and snow are on the horizon, starting Friday and continuing through Sunday, he said. Fresno’s forecast is for about 1 inch of rain through Sunday, with more rain falling in the foothills and lower Sierra elevations like Shaver Lake.

Snow will fall as low as 7,000 feet during the weekend storm, with as much as 18 inches of snow at higher elevations and a few inches at lower elevations, Bagnall said.

CHP Winter Driving Safety Tips