The remnants of a tropical storm that brought steamy rain and a volatile atmosphere to the Bay Area last week have faded, according to the National Weather Service. Next up are two rainy systems — the more traditional kind.
“We’ve got low pressure from the Gulf of Alaska moving on down,” NWS meteorologist Brayden Murdock said Monday. “One will come through, and we’ll get rain. We’ll get a pause. Then we’ll get the second one.
“The main rain bands hit up close to the North Bay and then will spread across the Bay Area. … It’s a pretty typical winter set-up.”
The arrival of the storms just as the region settles into autumn is not unusual, Murdock said. It’s simply an indication that the weather pattern has cleared itself of the tropical influence that brought hundreds of lightning strikes amid muggy, warm temperatures and isolated storm cells last week that dumped brief outbursts of heavy rain.
A bit of rain ahead of that first cold front carried tiny warmth left over from those tropical conditions. That rain scattered in small isolated cells north of Santa Rosa late Monday morning, ahead of colder, lower pressure coming from the Pacific Northwest anticipated by the weather service later Monday.
Even colder low pressure is anticipated to follow that first wave of cold and low pressure, Murdock said.
As a result, the rain this week is likely to be far more steady and less isolated, as well as considerably less intense.
“There’s not going to be a lot of it,” Murdock said. “But what we have is gonna be steady.”
Murdock said the rainfall, expected to begin Monday afternoon, is likely continue into Tuesday. A pause in the rain will hit at some point on Tuesday, but more low pressure will arrive later and bring scattered showers Tuesday evening into Wednesday.
Forecasters for the weather service predicted the most rain will fall on Mount Tamalpais in Marin County, where an inch is forecast. Areas of Sonoma County may get a half-inch from the two systems, according to the weather service. That part of the region also has about a 50% chance to see thunderstorms, according to the weather service.
The rest of the region is expected to see considerably less rain, with totals in Contra Costa and Alameda counties expected to fall between five-hundredths and one-tenth of an inch. That rain is expected to come without threat of thunder or lightning.
Cloudy, gray weather is expected to persist Thursday, even as the last of the rain chances for these two systems evaporate, Murdock said. On Friday, a warm-up that is expected to have the warmest places hit 80 degrees is supposed settle in and last at least through the weekend.
