Cloudy, Cooler Outlook : Clear, Sunny Days Head for a Weekend Fade to Gray

The clear, warm autumn sunshine that has bathed San Diego for several days is expected to be gone by the weekend, replaced by clouds and lower temperatures.

“We’ll see increasing clouds beginning today, with partly cloudy skies throughout the weekend,” National Weather Service forecaster Dan Atkin said.

Instead of coastal temperatures that ranged in the high 70s and low 80s during most of the week--a result of a weak Santa Ana condition--temperatures today are expected to decrease to the low 70s, with Saturday’s high predicted not to reach any higher than 68.

The cooling trend is the result of a weak high pressure system slowly moving east, Atkin said.

“This weak high pressure will bring early morning low clouds, fog and cooler temperatures through Sunday,” Atkin said.

With the lower temperatures, San Diegans can also expect humidity levels to rise some this weekend. Thursday’s afternoon humidity measured 34%, which is below the average of 60% for this time of year, according to Atkin.

“Humidity levels are expected to climb to 50% to 60% today and continue to be up throughout the weekend,” Atkin said.

Coastal areas will experience morning low clouds and some fog through Sunday. Today’s high will range from 70 to 74 degrees with lows in the mid-60s. High temperatures Saturday will range from 65 to 68 degrees, though they are expected to rise slightly on Sunday. Lows will be in the 55- to 60-degree range both days, according to Mike Smith, a meteorologist at WeatherData, which provides forecasts for The Times.

The ocean temperature is expected to be about 63 degrees, with surf of three to five feet predicted through Sunday.

Inland valleys will have highs between 75 to 80 degrees today, falling to the 69- to 75-degree range Saturday and Sunday. Lows will be between 48 and 55 degrees through Sunday.

Winds of up to 35 m.p.h. are expected to whip through mountain areas. High temperatures will range from 55 to 65 degrees through Sunday. Lows tonight are expected to dip to the 32- to 40-degree range, warming slightly Saturday and Sunday to 45 to 55 degrees.

Deserts will be mostly fair with winds gusting up to 35 m.p.h. today and Saturday. Highs will be in the upper 80s through Sunday. Lows will range from 50 to 58 degrees.