(NEW YORK) — A powerful Pacific jet stream is bringing two dangerous storms fueled by an atmospheric river to the West Coast, the first of which struck Northern California on Wednesday and is pummeling Southern California on Thursday.

This first storm brings a “significant threat to the safety of Californians,” Brian Ferguson, spokesman for the state’s Office of Emergency Operations Services, warned Wednesday.

The rain reached the San Francisco Bay area on Wednesday and has since dropped 3 to 5 inches of rain in Northern California.

Flash flooding was reported overnight and wind gusts topped 70 mph, knocking down trees.

The rain started in Southern California Wednesday night and is at its heaviest Thursday morning.

The heavy rain and winds are stretching from Santa Barbara to Los Angeles, with flash flooding in the forecast for Los Angeles during the morning commute.

The heavy rain and flash flooding threat will reach San Diego later in the morning, with showers lasting into the afternoon.

Cal Fire’s Nick Schuler encouraged Californians to have an evacuation plan, a full tank of gas and a packed “go bag.”

“Do not drive through moving water, and most importantly, if you are asked to evacuate, please do so without hesitation,” Schuler said.

The second storm will strike California on Saturday afternoon and last through Wednesday.

The heaviest rain will hit from San Francisco to Santa Barbara Sunday night.

Southern California will face its heaviest rain from Monday morning to Tuesday night. Flash flooding, mudslides and rock slides are expected.

Rainfall totals in Southern California are forecast to reach 3 to 5 inches along the coast and 5 to 10 inches in the mountains.

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