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A flash flood warning was issued Saturday for Northeastern Los Angeles County due to heavy rain and thunderstorms in the Antelope Valley area, forecasters said.

The warning is in effect until 6 p.m., with the Llano and Lake Los Angeles areas expected to experience flooding, according to the National Weather Service.

“Flash flooding is ongoing or expected to begin shortly, especially over highways 138 and 18 near Llano,” NWS said in a 1 p.m. alert.

The region had seen up to three inches of rain by 3 p.m., according to to NWS.

Officials said streets, underpasses, small creeks and other low lying areas could flood.

Radars detected thunderstorm activity “rapidly developing” in northeast area of San Gabriel mountains near Big Pines, extending into adjacent foothills of Antelope Valley around noon.

At the time, weather officials said the conditions, along with very gusty and erratic winds, could mean dry lightning that may result in new fire ignitions.

The warnings come amid a heat wave scorching Southern California and with several wildfires burning, including the Lake Fire in the Angeles National Forest area.

Photos showed a large plume over the Lake Fire, with NWS saying it’s due to “strong surface heating and an unstable atmosphere.”

“Very hot and unstable conditions will bring potential for deep vertical plume growth with existing and new wildfires today. Extreme fire behavior at times with potential for strong downdrafts, with rapid and large fire growth,” NWS Los Angeles said.