Last of the Bay Area rain to give way to dryer, colder weather pattern

A weather pattern that has brought steady rain to the Bay Area and coincided with the the biggest tides in nearly 30 years is about to shift into one that will dry out the region and usher in more chilly weather.

But first comes one final day of rain and flooding concerns, according to the National Weather Service.

“We’re going to have isolated to scattered showers throughout (Monday), and it’s going to be tapering off in the evening or probably even later at night,” NWS meteorologist Roger Gass said. “There’s also a chance for thunderstorms, but we’re on the low end there.”

The rain has been falling since New Year’s Eve and was especially heavy over the weekend, a period in which the rainfall totals were anything but on the low end.

As of Monday morning, areas of Santa Cruz County had received between 5 and 6 inches of rain since Friday, according to the weather service. Elsewhere, Mount Tamalpais in Marin County received about 4 inches; Santa Rosa received 2.07 inches; San Francisco International Airport had 1.88 inches and San Jose 1.37 inches.

Also since Friday, 1.17 inches fell at the Oakland San Francisco Bay Airport, 1.02 inches fell in Livermore, 0.87 inches fell in downtown San Francisco and 0.85 inches fell in Concord.

That rain coincided with king tides — a phenomenon in which the Earth, the moon and the sun all align and create a gravitational pull — that were fueled by a super moon and spilled 2½ feet further onto land then usual. That inundation was the highest by waves since 1998 and the fourth-highest in the region ever, Gass said.

Those waves already have begun to recede, according to the weather service. But they will continue to have an impact on Monday. A coastal flood advisory that runs from San Francisco to Cloverdale remained in effect until 3 p.m.

The beaches are expected to remain hazardous Thursday and Friday.

“Essentially, they’re done,” Gass said of the king tides. “We’re still having high tides as a result of the storm surge. It won’t be as high. The inundation is expected to be about 1.2 feet.”

In the Sierra Nevada, the snow also was expected to begin tapering off, though light to moderate snow showers are expected through Monday. The Lake Tahoe Basin is expected to get about 2 inches of snow.

The weather service downgraded a winter weather warning to an advisory that was set to expire at 10 a.m. in the Greater Lake Tahoe area. That advisory was set to remain in place until 7 p.m. in Lassen, East Plumas and Sierra counties.

Once the storms move south, the dryer pattern is expected to take hold.

“We’re finally going to be drying out, and we’ll have a dry weekend ahead,” Gass said. He added that the weather service anticipates the dry weather will last “at least seven days.”

The new air mass is expected to make the temperatures quite chilly. Overnight low temperatures are expected to fall into the 30s in the East Bay and North Bay valleys and into the mid to low 40s elsewhere in the region. The high temperatures during the day are not expected to exceed the mid-50s anywhere.