(TNS) - Rain continued to soak Santa Barbara and Ventura counties Wednesday afternoon as residents of fire- and mudslide-battered communities endured the first day of Southern California's largest storm of the season.

The storm — a vast atmospheric river of tropical moisture known as a "pineapple express" — made landfall Tuesday night and is predicted to last through Thursday.

"It's going to be steady, light rain with periods of heavy rain," said Stuart Seto of the National Weather Service in Oxnard. Heavier bouts of rain will occur Wednesday evening and the following day, he said.

By Wednesday afternoon, rain-triggered slides forced Amtrak's Pacific Surfliner train to stop south of Carpinteria as Union Pacific maintenance crews removed debris from the tracks. The railway was cleared after an approximately 45-minute delay, Amtrak said.forced

The rain comes just months after the Thomas fire scorched more than 440 square miles of land, reducing thick forest and chaparral to ash and making steep hillsides susceptible to mud and debris flows. Residents who live below the Thomas fire burn area, as well as the Sherpa and Whittier fires were told to evacuate their homes by noon Tuesday.

Flash flood watches were issued in Santa Barbara and Ventura counties, where scorched hillsides will start to dissolve into mud flows if it rains at a rate of more than half an inch an hour, according to the U.S. Geological Survey.

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