One final burst of rain expected in Bay Area before a cold snap takes hold

The end appears to be in sight for a seemingly endless flow of rain that again was expected to stream down steadily on the Bay Area for at least part of Tuesday, according to the National Weather Service.

Next up on the weather menu: dry, cold air.

“The winds from the northwest are going to build, and that’s going to be helpful in drying out the rain,” NWS meteorologist Rick Kaplan said early Tuesday. “The pattern itself is continuing to shift south, so by late morning or late afternoon, we really should start to see the beginnings of the wet stuff tapering off. That’s also going to allow the cooling pattern to begin.”

It’ll be a significant change following nearly a week of almost constant rain. It fell steadily again Monday throughout the region, though with a bit less intensity than it did when an atmospheric river system first hit the area.

In the 24 hours ending Tuesday at 6 a.m., about six-tenths of an inch fell on Ben Lomond and Mt. Umunhum in the Santa Cruz Mountains, the highest totals in the region. San Jose and Mountain View received about a quarter-inch in the South Bay, as did Danville and Richmond in the East Bay. Oakland received about two-tenths of an inch.

Including Sunday, San Jose had received about .44 inches of rain in a 48-hour period ending at 6 a.m., while Livermore had about one-third of an inch, San Francisco a quarter-inch and Oakland about two-tenths. About three-quarters of an inch fell on Mount Diablo in that 48-hour stretch.

Now, with the winds shifting, the system bringing the rain will accelerate out of the region, Kaplan said. It will be replaced by extremely cold air.

“You’ve got some high pressure moving aloft, and that’s going to advance toward the Bay Area from the Pacific Northwest,” Kaplan said.

The result is expected to be high temperatures that stay in the low 60s and 50s throughout the region and overnight temperatures that could get as low as 32 in some areas. The weather service issued a frost advisory from 10 p.m. Wednesday until 9 am. Thursday for the East Bay hills and valleys; the eastern Santa Clara County hills; the Salinas and Carmel valleys; San Benito and Monterey counties; and the North Bay interior.

“You’ve got some high pressure moving aloft, and that’s going to advance toward the Bay Area from the Pacific Northwest, and that’s going to bring the cold air,” Kaplan said.

The cold snap is expected to last at least through the weekend, according to the weather service.