(NEXSTAR) – Here we go again. Another atmospheric river is heading toward California, preparing to dump heavy rain and snow over the state.

While rain was already falling in parts of California on Wednesday, the main event is expected to start Thursday, National Weather Service forecasters say. The heaviest rain will likely fall Thursday night into Friday, when activity will peak, but precipitation is expected to continue through the weekend.

The ground is already saturated in many parts of the state, and flooding risk remains high through Sunday.

But even after the atmospheric river passes, the forecast doesn’t look dry. In San Francisco, there’s at least a 50% chance of showers through Tuesday.

In fact, it could be weeks, or even a month, before we see a stretch of dry weather in the region, said Brian Garcia, warning coordination meteorologist with the National Weather Service’s Bay Area office. It’s hard to forecast that far out, Garcia acknowledged, but said there wasn’t dry weather on the horizon “for the next couple weeks.”

“If we go deep into the crystal ball, then the week of the 27th we might have a few sunny days, but in all likelihood, we won’t dry out until we get deep into spring and early summer,” he told Nexstar. “This is a prolonged pattern that we are entrenched in and look to remain so for March and possibly into April.”

The rain will at least give folks in Los Angeles and San Diego a little break. Both cities are expected to see some sun Sunday and Monday.

Atmospheric rivers have gotten a lot of attention this winter for a few reasons. First, they have a bigger impact than your average rainstorm. An atmospheric river, also sometimes called “pineapple express,” picks up moisture near Hawaii, then blows toward the Western U.S. The long stream of moisture – which essentially looks like a river in the atmosphere – can dump rain and snow for days.

The second reason we’re talking about atmospheric rivers so much is that they keep on coming. Late last year into January, a series of back-to-back storms flooded towns, triggered mudslides, opened up sinkholes and caused at least 17 deaths.

KRON On is streaming live news now

In Northern California, the Sierra Nevada mountains and surrounding communities were under a winter storm warning through the weekend. At elevations above 6,500 feet, 2 to 5 feet of snow is possible between Thursday and Sunday.

Heavy rain and snow mixed with high winds could also make driving treacherous. Warm temperatures also mean snow melt is more likely, increasing the risk of avalanches in areas where there is deep snow, the NWS said.

Central Valley communities, from Merced down to Bakersfield, are also at risk of flooding for overflowing rivers and creeks.

In Southern California, this storm system poses the biggest threat to San Luis Obispo and Santa Barbara counties, the National Weather Service’s Los Angeles office warned.