The NWS warned that extensive street flooding and flooding of creeks and rivers are possible.
The seasonal average there is 17 inches.
Heavy winds will accompany the storm, with the DWP warning of gusts between 40-60 mph.

Downtown Los AngelesGary Coronado / Los Angeles Times via Getty Images
Travel could be very difficult to impossible, according to NWS.
Very strong winds could cause extensive tree damage.
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Thunder and lightning are possible on the back side of the system.

NWS