The Weather : A Beach Weekend Shapes Up

Southern California’s weekend will be mostly warm and dry--just like the rest of the week--except for seasonal thundershowers along the Arizona border, forecasters said Thursday.

Cary Schudy, meteorologist-spokesman for Earth Environment Service, a private forecasting firm based in San Francisco, said a deep low-pressure system that has been hanging over the Pacific Northwest for a couple of weeks is beginning to break down.

High-Pressure System

“This will open the way for high pressure at upper levels in the atmosphere,� he said. “So the days should be drier and warmer. A big influence along the coast, though, is the upwelling of ocean waters that normally occurs at this time of year.

“The water that comes up from the ocean’s depths is very cold, so it causes the moist air to be cooler--and you get dense morning fog and low clouds.

“This year, however, the upwelling has been very weak, so the effect on the air is minimal and the skies clear up very early in the day.�

High temperature at Los Angeles Civic Center on Thursday was 88 degrees, with relative humidity ranging from 87% to 35%, and the National Weather Service said the weekend should be about the same.

The sun was expected to break through clouds along the beach by mid-morning each day, with afternoon temperatures in the mid-70s in most places, surf running two to four feet on a 12-second interval (west-facing beaches could see a few five-footers) with a 16-knot sea breeze each afternoon and water temperatures in the mid-60s.

Winds Out of West

Weekend seafarers should see westerly winds rising to 12 knots with two-foot seas most afternoons in the inner waters from Point Conception to the Mexican border. But a small-craft advisory was in effect Thursday for outer waters south of Santa Rosa Island, with west to northwest winds in the 15-knot range and a six-foot northwest swell combined with three-foot seas.

Mostly sunny weather was expected for the Southern California mountains, with afternoon highs to the mid-80s, but forecasters said there was a chance of afternoon thundershowers over the eastern deserts, with southwest winds to 25 m.p.h. in the afternoons and evenings. High desert temperatures were expected to range from the mid-90s to 106 degrees, with the low desert about 10 degrees hotter.