The heaviest Bay Area storm system in a string of three of them is forecast to bring with it Tuesday everything that might be expected in the dead of winter.
Clouds will look even darker and thicker. Winds will whip with ever-increasing speed. Flood waters likely will rise. Rain should pelt much of the Bay Area region.
Even thunder, lightning and small hail are possible.
“The heaviest rain is still offshore and on its way,” National Weather Service meteorologist Ryan Walbrun said early Tuesday, even as moderate rain already was falling in many places. “It’s going to keep on increasing throughout the day, and the afternoon commute is probably when the heaviest of it will move through. So yes, the heaviest rain is still to come.”
Rain has been falling off an on in the region since last Friday, the first measurable rain outside the North Bay since Jan. 3. But Walbrun said that outside the North Bay, the precipitation has not fallen as hard as it probably will Tuesday.
This system, which Walbrun said is carrying characteristics of an atmospheric river, also may bring some thunderstorms, lightning and some small hail, he said.
“We’ve got a lot happening with this one,” Walbrun said.
The weather service issued a flood warning for areas of the Russian River near Guerneville, and a flood watch for the region that started Monday remained in effect until 4 a.m. Wednesday. The agency also issued wind advisories, with Walbrun saying the lightest gusts in the region are expected to be 35 mph. Walbrun said the gusts are likely to reach as high as 60 mph in the higher elevations.
On Monday, it rained steadily off an on, with the North Bay again getting the bulk of it. Kentfield in Marin County received 3 1/3 inches of rain over a 24-hour period ending at 7 a.m., while 2¾ inches fell in San Rafael, according to the weather service.,
Slightly more than 1¾ inches of rain fell in Saint Helena in Napa County, and another 1½ inches fell in Santa Rosa in Sonoma County.
In Contra Costa County, Richmond received 1¼ inches of rain over the same 24-hour period, and Orinda had slightly less than an inch. Three-quarters of an inch fell at the Oakland Airport, and a quarter-inch fell in Hayward.
The South Bay received considerably less, with .08 inches falling in Palo Alto and .05 inches measured at San Jose Mineta International Airport.
The system arriving Tuesday figures to bring totals that will be higher in most places, though the North Bay may get a bit of a reprieve, according to Walbrun.
“It will end pretty abruptly (Tuesday) evening after it passes through, especially in the North Bay,” he said. “Then Wednesday is a dry day, as we get a break between systems. Rain is then gonna re-develop again on Thursday.”
The Thursday storm is forecast to be the last one created by the current pattern. Walbrun said the weekend is expected to be dry and chilly, with high temperatures staying in the 50s. Clouds are likely to depart the area over the weekend.