Smog Alert Called in Northern County

Coastal fog that pushed its way inland caused a first-stage smog alert in portions of northern Orange County on Sunday after it mixed with smog trapped by a high pressure system that is expected to remain until Wednesday.

“Low clouds are being kept close to the ground because of a shallow inversion layer that is making the clouds produce the fog,” said Stephen Burback, a meteorologist for WeatherData Inc., which forecasts the weather for The Times.

Burback said the high pressure system will remain over Southern California for at least another day, creating the unusual fog-and-smog mixture that wreaked havoc with Orange County motorists over the weekend.

Once the fog lifts, high temperatures are expected in the low- to mid-80s, with some cooling expected by mid-week, Burback said.

On Sunday, Santa Ana reported a warm 83 degrees after the fog lifted. Newport Beach, which spent much of Sunday under a thick blanket of fog, was 68 degrees.

Anaheim had a high of 85 and San Juan Capistrano had an 81.

In Brea, morning fog gave way to a smoggy afternoon “that never cleared up,” said Brea Fire Department Capt. Paul Bartley.

Although the air quality was unhealthful, it resulted in few calls from residents with respiratory illnesses, Bartley said.

The South Coast Air Quality Management District posted the first-stage smog alert at 3 p.m. Sunday after the Pollutants Standard Index (PSI) level reached 205. The PSI measures the amount of pollutants in the air, whether ozone, carbon monoxide or nitrogen dioxide.

“Unhealthful for sensitive people” warnings occur when the PSI registers from 101 to 199. A first-stage smog alert, meaning the air is unhealthful for everyone, occurs when the PSI registers 200 to 275.

The high-pressure system should start shifting east by mid-week, Burback said, and Hurricane Trudy, which brought three- to five-foot breakers on south-facing beaches over the weekend, is also expected to help clear out the smog.

Trudy, with winds well over 100 knots, is about 1,000 miles west of the tip of Baja, Mexico, and about 1,200 miles south of Southern California.

“The lid holding the pollution and the fog would be pretty much gone in maybe one more day, or possibly a second day before a northern storm moves down the coast,” Burback said.