Update 6:50 p.m.: A flash flood advisory will continue through 8 p.m., according to the National Weather Service.
An urban and small stream flood advisory is in effect for central Los Angeles County, including Sunland, Tujunga, La Crescenta, La Canada Flintridge, Altadena, Sierra Madre, Monterey Park, Downtown Los Angeles and Long Beach.
Showers and thunderstorms are expected across the San Gabriel Mountains and Los Angeles County where minor urban flooding could happen, especially near small drainages.
Forecasters urge commuters to avoid hydroplaning and turn on headlights in the rain.
Earlier: The National Weather Service issued a flash flood warning Thursday afternoon for L.A. County, with specific warnings about heavy rainfall in the San Gabriel Mountains.
The full warning is listed below:
...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 700 PM PDT FOR CENTRAL LOS ANGELES COUNTY... AT 435 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO INDICATE A STRONG THUNDERSTORM PRODUCING FLASH FLOODING ALONG ALISO CANYON ROAD IN THE SAN GABRIEL MOUNTAINS A FEW MILES SOUTHEAST OF ACTON. VERY HEAVY RAINFALL HAS BEEN CONFIRMED IN THIS AREA BY A RAIN GAUGE REPORTING OVER TWO INCHES IN ONE HOUR...WITH A STORM TOTAL EXCEEDING 2.5 INCHES. THIS STORM CONTINUES TO HAVE LITTLE MOVEMENT AND IS BACKBUILDING TOWARD THE SOUTHWEST ACROSS THE MOUNTAINS. EXPECT FLASH FLOODING IN THIS REGION WITH WATER RUNOFF AND POSSIBLE DEBRIS AND MUD FLOWS ACROSS ROADWAYS THROUGH 7 PM PDT.
PRECAUTIONARY/PREPAREDNESS ACTIONS... DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS SAFELY. MOVE TO HIGHER GROUND. MOST FLOOD DEATHS OCCUR IN AUTOMOBILES. NEVER DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE ROADWAY. FLOOD WATERS ARE USUALLY DEEPER THAN THEY APPEAR. JUST ONE FOOT OF FLOWING WATER IS POWERFUL ENOUGH TO SWEEP VEHICLES OFF THE ROAD. WHEN ENCOUNTERING FLOODED ROADS MAKE THE SMART CHOICE...TURN AROUND...DONT DROWN.