Thundershowers Hit Desert, Mountain Areas in 3 States

Sudden and intense thundershowers pelted the deserts and mountains of Southern California, Arizona and Nevada on Monday in the wake of an invasion of moist, unstable air from Mexico.

By midafternoon rain, lightning and winds gusting to 30 m.p.h. at times were reported from Winkelman, Ariz., where .73 of an inch of rain fell in just 30 minutes, to Mt. Laguna in San Diego County, which received 1.65 inches.

Palomar Mountain reported .75 of an inch by late afternoon, while the mountain community of Julian received .65, and Borrego, in the desert, had .41.

Flash-flood watches were in effect for Los Angeles, San Bernardino, Riverside, San Diego, Kern, Inyo and Imperial counties in California and for the western parts of Nevada and Arizona.

Expected to Dissipate

The National Weather Service said the watches would probably remain in force overnight, although most of the violence was expected to dissipate before dawn today.

Meteorologists blamed the bad weather on the sudden development of a weak low-pressure area over Southern California, which invited an influx of marine air flowing out of a high-pressure ridge centered about 400 miles west of Seattle and extending north and south across the eastern Pacific.

Forecasters said the general instability could last through today, with high and low clouds, a few coastal showers and occasional local thunderstorms--accompanied by brief but intense wind activity--gradually easing away to sunny skies by Wednesday.

High temperature at Los Angeles Civic Center on Monday was 79 degrees, with relative humidity ranging from 54% to 90%. Today was expected to be two or three degrees warmer, but no drier, with temperatures returning to the mid-80s by Wednesday.