SAN FRANCISCO — El Nino storms lined up in the Pacific, promising to drench parts of the West for more than two weeks and increasing fears of mudslides and flash floods in regions stripped bare by wildfires.

Stronger systems are predicted starting Tuesday following light rain a day earlier. At least two more storms are expected to follow on Wednesday and Thursday, possibly bringing as much as 3 inches of rain.

The National Weather Service issued a flash-flood watch for Northern California communities affected by several destructive wildfires last summer and fall.

The brewing El Nino system — a warming pattern in the Pacific Ocean that alters weather worldwide — is expected to impact California and the rest of the nation in the coming weeks and months.

In recent weeks, a weather pattern partly linked with El Nino has turned winter upside-down across the nation, bringing spring-like warmth to the Northeast, a risk of tornadoes in the South, and so much snow across the West that even ski slopes have been overwhelmed.