Light showers greeted San Diegans Thursday morning but this isn’t the extent of the series of storms that the National Weather Service describes as the "largest rain event" in Southern California since March 2011.
On Thursday, rain will taper off in the afternoon hours. Then, another major storm will arrive.
Heavy rain is expected Friday afternoon. To help residents prepare for this unusual amount of precipitation expected, the NWS has issued a flood watch beginning in the early morning hours of Friday and extending through Saturday.
Flash flooding may occur in the mountains and recent burn areas. Some valleys and areas prone to flooding – like the San Diego River in Mission Valley - and those urban areas with poor drainage will see excess water.
Some thunderstorms are expected as well.
There's a coastal flood watch issued with widespread minor coastal flooding expected Friday and Saturday during times of high tide. Residents and businesses in La Jolla, Cardiff and Imperial Beach should be prepared for the possibility of minor flooding.
The highest high tides are expected Friday morning.
Strong rip currents, elevated surf heights and lightning will create dangerous conditions for swimmers and surfers off San Diego's coast, forecasters warn.
To help residents prepare for damage from flooding, the county is offering free sandbags at several locations. San Diego firefighters and the City of Escondido have also distributed a list of locations where residents can pick up the bags.
On Thursday, the weather system moved down from Northern California, bringing up to an inch of rain in drought-stricken coastal and valley areas of Los Angeles County, and more in the mountains.
About an inch of rain fell earlier around the San Francisco Bay Area.
The storm -- and the far larger one expected to arrive Friday -- brought worries and recommended evacuations in some areas in the suburbs of Glendora and Azusa about 25 miles northeast of Los Angeles, because they sit at the foot of the steep San Gabriel Mountains where a wildfire last month stripped nearly 2,000 acres where water could now pose a danger.
A high wind watch is also in effect through Saturday for San Diego County mountain and desert areas.
San Diego Gas and Electric wants to remind customers they should always assume that power lines are energized. Report any downed lines to 911 and SDG&E immediately at 1-800-611-SDGE (7343).
To make sure you’re prepared, download NBC 7’s free app for breaking news alerts throughout the storm and our new free NBC 7 Weather app for radar and forecast anytime, anywhere.