LOS ANGELES — Much-needed rain fell across Southern California on Tuesday but in lighter amounts than originally forecast for the region, which has experienced a very dry winter.
San Diego County mountains already had received an inch of rain before dawn but generally the precipitation was showery rather than steady, and the National Weather Service adjusted expected totals downward.

“Slow start to the storm this morning,” the Los Angeles-area weather office tweeted.
The rain was being caused by a low pressure system off the coast of Southern California and Baja California that was drawing a plume of subtropical moisture northward, meteorologists said.
Showers were expected to increase as the low approached but satellite imagery showed the atmospheric river was carrying most of the moisture into Baja California.
Despite the reduced rainfall expectations, forecasters cautioned that potentially strong thunderstorms, and potential roadway flooding and debris flows from burn areas, were a possibility through the day from Los Angeles County and up the Central Coast to San Luis Obispo.
North of the Los Angeles region, a flash flood watch was also in effect for the mountains and desert of Kern County, and a winter weather advisory was issued for a small portion of the southern Sierra Nevada.