Mostly cloudy and cooler conditions across San Diego County will prevail Sunday ahead of an approaching Pacific storm system, with rain and mountain snow beginning late Sunday night and continuing at times through Monday night, the National Weather Service said.
A winter storm warning was issued by the NWS from 8 a.m. Monday to 4 a.m. Tuesday for San Diego County mountains.
A high surf advisory was issued until 10 a.m. Wednesday for county coastal areas. A small craft advisory will be in effect from 3 a.m. Monday to noon Tuesday for county coastal waters.
High temperatures along the coast Sunday were expected to be around 63 degrees with overnight lows of 45-50, with a chance of rain, the NWS said. Valley highs will be 62-67 with overnight lows of 40-47 and a 50% chance of rain.
Mountain highs were expected to be 56-62 with overnight lows of 31-38 and a 50% chance of rain and snow. The snow level was expected to be at 5,000 feet. Highs in the deserts will be 67-72 with overnight lows of 40-50 and a 20% chance of rain with wind gusts of 30-35 mph.
The storm system will bring precipitation starting late Sunday night, mostly after midnight, forecasters said, with the first wave a little ahead of what was previously expected, mostly before sunrise Monday.
Monday's rain showers could be briefly heavy, and snowfall will prevail in the mountains through Monday night with difficult travel conditions, forecasters said. Rainfall rates could get up to around 0.40 inches per hour.
"The storm will move east on Tuesday, followed by gusty, dry, northerly winds Wednesday," the NWS said. "Temperatures will mostly be below normal until around the New Year."
Winds will turn briefly back onshore around Thursday before turning back offshore New Year's Day when Santa Ana conditions will be possible, the NWS said. Temperatures should increase a bit starting Friday.
At county beaches, forecasters said a building west swell was expected to raise surf Sunday, with widespread elevated surf conditions likely, and a few sets to 7 feet possible. Surf will increase on Monday, peaking between Monday afternoon and Tuesday, with sets to 8 feet. In southern San Diego County, sets might reach 9 to 10 feet Monday and Tuesday.
There will also be a chance of thunderstorms with lightning on the beaches on Monday.
