You Can Blame the Rain on a Rocky Mountain High

A swirling high-pressure front sitting above the Rocky Mountains pushed gray skies and drizzle into Orange County on Tuesday, but forecasters said the damp weather should be gone today or Thursday.

The high-pressure zone that was above Utah and moving into Colorado on Tuesday was pulling tropical moisture from the gulfs of Mexico and California and pushing it northwest--a common summer phenomenon called a monsoonal effect.

While the mountain high-pressure activity will likely last through the summer, its effect on Southern California should subside this week, said John Sherwin, a meteorologist with WeatherData, which provides forecasts for The Times.

“Imagine the center of a wheel sitting above the Rockies, spinning clockwise and picking up moisture in east Mexico and carrying it into the desert southwest and California,” Sherwin said. “At its current position, it’s shooting all that into California, but it’s already moving east.”

Sunnier skies should prevail by Thursday as the monsoonal effect relents, according to Mel Newman, a county environmental resources specialist who monitors local rainfall. Sherwin predicted the clear skies would arrive today.

Although gauges throughout Orange County showed less than 0.04 of an inch of actual rainfall Tuesday, Sherwin said “moisture at all levels” made for slick roads and deserted beaches.

The California Highway Patrol said there did not appear to be an increase in accidents Tuesday on local freeways.

The dreary weather produced more intense results in nearby counties. In San Diego, officials issued a flood advisory for urban and small streams, while more than an inch of rain was logged in Riverside, Sherwin said.