Possibly an inch of warm rain expected today; cooler wet weather this weekend

SAN DIEGO - Up to an inch of warm rain is expected throughout San Diego County today ahead of cooler but more scattered wet weather this weekend, forecasters said.

A low pressure trough about 400 miles west of San Diego will draw warm, moist subtropical air into Southern California through this evening, according to the National Weather Service. The agency said there would be brief periods of heavy rain and isolated thunderstorms as the chance of rain increases throughout the day.

''The rain chances will increase tonight and remain high through tonight as the center of the trough moves closer,'' according to an NWS advisory. ''Rain chances decrease Saturday as the trough moves east.''

The weather service said there will still be showers on Saturday behind the trough but the rain will not be as widespread as today. Most of the showers Saturday will be over the mountains, according to the weather service.

''On Sunday and Monday, a second, colder low pressure trough from the north will bring cooler, breezy weather and a chance of showers,'' forecasters said. ''However, this is a drier system so the showers will be less widespread. Greatest impacts from this second system will be the colder weather, gusty winds and lower snow levels down to 4,000 feet by Monday morning.''