Lengthy spell of rain is on the horizon for Bay Area

'Conga line of storm systems' will start to arrive on Friday

An encouraging development is on tap for the Bay Area following months of dry weather that has been interrupted only on rare occasions.

A decent amount of rain is on the way.

“We’ve got a conga line of storm systems,” National Weather Service meteorologist Drew Peterson said.

That line will begin arriving late today and into Saturday and will signal a significant change to the general weather pattern that has brought warm temperatures and, for a couple days, powerful winds. It’s the first of two small systems expected to pass through the Bay Area by the end of the weekend, according to the weather service.

The first two systems will bring only light showers. But two bigger ones will follow after that.

“The first two that we have on the way are going to be a prelude to the much bigger event arriving next week,” Peterson said. “The bigger events have the potential for a higher-end ‘atmospheric river’ kind of event.”

Atmospheric rivers tend to be weaker systems but carry heavier amounts of precipitation, according to the weather service.

“The main concern for that would be the high rate of rainfall,” Peterson said. “That could affect the burn areas that are still recovering from the fires last summer.”

The first approaching system already is having an effect on temperatures, which rose into the high 70s throughout the region earlier this week, setting records in some cities. On Thursday morning, temperature readings were in the low 30s throughout the region — the thermometer fell to 29 degrees in San Ramon — and they weren’t expected to escape the 60s during the day.

“It’s going to continue to be pretty cold,” Peterson said.

The first of the two systems should arrive in the North Bay and begin to spread south through other areas of the Bay by Saturday morning. The North Bay will receive the brunt of that small rain, though areas in the Santa Clara, Alameda and Contra Costa counties are expected to get anywhere from five-hundreds of an inch to onethird of an inch, Peterson said.

A second system should arrive by Sunday morning. The stronger systems are expected to reach the Bay Area by Wednesday, and Peterson said the rainfall will be significantly higher.

In all, the different systems could keep rain falling relatively consistently for 10-14 days, according to the weather service.

“With everything being dry,” Peterson said, “we’ll take everything we can get.”