A weak low-pressure system along the coast will keep San Diego County seasonally dry and warm Sunday through midweek, forecasters said.

Low pressure will be replaced by a building high-pressure system over the Southwest later this week, bringing a heat wave inland by next weekend, the National Weather Service said. Onshore flow should still moderate coastal areas, but temperatures will likely be above average.

Sunday’s high temperatures along the coast will be 71-76 degrees with overnight lows of 58-63, the NWS said. Inland highs will be 79 with overnight lows 56-61. Western valley highs will be 79-84 and near the foothills, 87-92.

Mountain highs will be 85-95 with overnight lows 53-63. Highs in the deserts will be 108-113 with overnight lows 71-81.

The marine layer offshore was widespread Sunday morning and extended inland up to 25 miles over western San Diego County, forecasters said.

“By midweek, a transition to warmer weather will be underway as the trough weakens and a ridge of high pressure builds over the Southwest,” the NWS said. “By next weekend, a strong high-pressure center aloft will be centered over the Lower Colorado River Valley. Daytime temperatures then could be 10 degrees or more higher than average over the valleys and deserts.”

Onshore flow should maintain moderate conditions over coastal areas based on the current forecast pattern, but a shallow marine layer will increase the chances for areas of dense fog later this week.

At San Diego County beaches, a building south swell will bring higher surf and stronger rip currents Monday through Wednesday. Surf will be from 3-5 feet with some sets to 6 feet in northern San Diego County. The surf will not be quite as large in southern San Diego County, generally 3-4 feet.

–City News Service

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