New weather stations are helping California forecasters better predict flooding from damaging storms called the 'pineapple express'

It wasn’t a drenching atmospheric river. But the biggest storm to hit the Bay Area in roughly seven months began to douse much of California on Monday afternoon, slowing motorists, dropping snow in the Sierra Nevada, and providing a clear signal that the winter rainy season has begun.

Bay Area residents are advised to prepare for upcoming widespread rainfall and potential thunderstorms next week.

Forecasters now have a big clue to what weather will look like in California this winter.

Looking at the total rain forecast, we anticipate that there will be at least an inch across the Bay Area and there could be up to 2-3 inches in the mountains and higher elevations. … This is probably going to be a pretty notable early season storm.

The big takeaway: Generally speaking, during La Niña winters, Southern California more often has had drier conditions than Northern California. Put another way, the farther north you go, the more likely it is to be wet during La Niña winters and the farther south you go, the more likely it is to be dry.

But the state's water experts say at this time of year, they still have to prepare for floods, drought or even both. Oct. 1 officially began the rainy season in California, and with this seasonal shift, they sealed their record of annual rain and snow and started a fresh tally.