A rare flash flooding event occurred in southern California earlier this afternoon as slow moving thunderstorms impacted areas east of San Diego. A trough in the Pacific is expected to move onshore on Tuesday, and southerly winds ahead of this trough are helping to pull monsoonal moisture into the desert southwest.
Check out the wide variety of flood products issued by the NWS San Diego office:
This monsoonal flow interacted with the mountains just east of the Pacific coast and produced thunderstorms with very heavy rainfall. Precipitable water values are currently 1.5-2″ which is very rare in the southwest.
Multiple flash flood warnings were issued as the storms dumped produced 1-4″ of rainfall in portions of southern California. There were multiple road closures due to the heavy rain and a flash flood warning was even issued for eastern San Diego county.
The flooding was very localized, 10-20 miles west of the warning skies were clear.
Additional rounds of thunderstorms are possible through Tuesday night before drier air moves in behind the trough.
Flash flooding is not the only excitement in southern California today. Tropical Storm Norbert is currently 440 miles south of San Diego and even though Norbert will stay well south of southern California, the tropical storm will cause elevated surf and minor coastal. A 4-6 foot swell is expected to move in today and tomorrow and a Beach Hazards Statement is in effect along the coast from Los Angeles to the Mexican border.
The trough in the Pacific will help steer Tropical Storm Norbert into Baja California. In the latest forecast from the NHC, Norbert is expected to weaken into a tropical depression and make landfall on Wednesday.