They asked to hear about what steps have been taken to prepare, saying they "hope that preparation and mitigation efforts are underway". Clean up is expected to continue into Friday as well, with emergency crews shoveling mud and debris off the road.
Southbound lanes were expected to open sometime around 5 p.m., according to CHP estimates.
Strong thunderstorms could produce heavy rain over the deserts and mountains of Los Angeles and Kern counties, forecasters say.
Meanwhile, Amtrak Thruway bus service between Los Angeles and Bakersfield was suspended for Saturday because of the problems on the 5 and state Route 58, Amtrak announced.
Thousands of cars and trucks were stuck in queues along the road, which runs the length of California. Vargas and dozens of other people spent the night stuck in the Tehachapi Pass area.
Mudslides that stranded almost 200 vehicles have closed a California highway that is a popular route from the Central Valley to Las Vegas. "There will be the potential for additional flash flooding as well as mud and debris flows across the watch area Friday afternoon into early evening".
With the increased chances of El Niño rains hitting California this year, schools are revisiting their safety and closure protocols, Sanders said, and will be making sure their campuses are prepared for rain.
Authorities said they hoped to reopen the Grapevine section later in the day, after geologists checked the stability of the adjacent hillside.
As much as 1.45 inches of rain fell in a short period of time around 3 p.m. in the area of the most intense flood.