Another day of unstable air remained on the Bay Area weather menu Thursday, with bitterly cold air from a storm pattern in the region mixing with warming temperatures closer to the surface that are paving the way to a clear weekend, according to the National Weather Service.
“We have a lot of relative instability, and that’s going to steepen even a bit more (Thursday) morning,” NWS meteorologist Rick Canepa said. “That’s going to lead to additional showers and it’s possible thunderstorms are in the mix.”
So it will be that measurable rain is expected to fall in areas of the region for a third consecutive day. The weather service said that rain again will be heaviest in areas of the South Bay, the Santa Cruz Mountains and the Central Coast but that the East Bay and North Bay won’t be excluded entirely .
Those two areas of the region were left dry on Wednesday, a day after receiving about two-tenths of an inch in the wettest places on Tuesday. A half-inch of rain did fall Wednesday in Ben Lomond in Santa Cruz County, while three-tenths fell at Mount Umunhum, two-tenths fell at Loma Prieta and a little more than one-tenth of an inch fell in San Jose, according to the weather service.
The atmosphere’s instability since Monday may be setting the month up to be a wet one, forecasters have said. But Canepa said any trend toward steady rain will take a pause beginning Thursday night and lasting through the almost the entire weekend. Another low-pressure trough bearing down on the region with more rain is likely to arrive late Sunday night, he said.
“It’s going to switch around pretty quickly Thursday evening,” Canepa said. “Upper-level high pressure is moving in from the west and the northwest, and that’s going to mean a quick clearing up by (Thursday night) that could leave some patches of fog Friday morning.”
It will be the mixing of that low pressure with the incoming higher pressure that could make for thunder and lightning, Canepa said.
By Friday morning, the high pressure will have taken a firm hold, Canepa said. Temperatures that have not reached the 60-degree mark for a week will begin creeping higher. They are expected to peak in the mid-60s in most places among what forecasters say will be entirely blue sky.