The National Weather Service has issued a flash flood watch for San Diego County out of concern that a Pacific storm could drop 2 inches of rain near the coast and 3 or more inches inland, mostly from late Friday night to early Saturday afternoon.
“Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations,” the weather service said in a statement. “Flooding may occur in poor drainage and urban areas. Low-water crossings may be flooded.”
The system, which is drawing lots of moisture from the subtropics, is currently producing scattered showers that will become stronger during the Friday evening rush hour and greatly intensify before dawn on Saturday, forecasters said.
The heaviest rain will fall east of Interstate 15 and could come in the form of brief but powerful thunderstorms that generate lightning. Winds could gust up to 35 mph.
UC San Diego says the atmospheric river feeding the storm will be a stage 3 event, meaning that it’s likely to be both beneficial and hazardous. The rain will greatly diminish the threat of fall and winter wildfires, but could cause mudslides.
It’s possible that the storm will be followed by two smaller systems through Tuesday that could bring San Diego’s total rain fall over a five day period to 3 inches, according to UCSD’s Center for Western Weather and Water Extremes.
That would be unusual because the region is in the midst of a weak La Nina, which are more commonly associated with below average rain.
Agencies across the county are providing sand and sandbags to residents for free. Find a list of locations on alertsandiego.org.