Storm Causes 3 Deaths, Closes Roads in Mountains : Weather: Two people missing in Sierra, three children in river. Snow ties up rush-hour traffic near Pomona.

Mostly fair and slowly warming weather is expected today and later this week in the aftermath of a bout of violent storms that caused the deaths Wednesday of a mother and child in Tijuana and the earlier disappearance of two snowmobile riders in the Sierra.

In Stockton, rescuers recovered the body of one of four children missing in a rain-swollen river.

The latest in a string of March storms brought heavy snows to the mountains and high deserts, dusted even such lowland areas as Pomona with snow and produced downpours and sporadically high winds in other areas.

Just west of Pomona, snow stuck on the Kellogg grade of the San Bernardino Freeway, causing two hours of disruptions around the morning rush hour, with the California Highway Patrol escorting traffic through the iciest areas.

Road closures were reported along Interstate 5 on the Grapevine, on California 18 near Big Bear and California 38 near Angelus Oaks, where avalanches struck, and on California 247 and 62 in the high desert near Yucca Valley, where two feet of snow fell.

All Southland ski areas, which through February had been suffering through one of the sparsest snow seasons on record, reported heavy snows and expected clearing of roads and fine skiing conditions this coming weekend.

But Wednesday, it was hard to reach the snow. Benno Nager, general manager of the Snow Valley ski resort, said: “It’s great. The skiing is really going to be very good. The bad side today is that the roads are all closed.”

Cleanup proceeded Wednesday at the site of a tornado that struck the Huntington Beach area late Tuesday night. Authorities reported 50 mobile homes in the Driftwood Trailer Park and 22 regular homes nearby were damaged by the twister. Police Lt. Jeff Cope said six homes lost their roofs.

Tornado-like winds also hit at San Marcos in San Diego County, and gusts in San Diego resulted in an injury to a motorist in Balboa Park when a tree fell on his car.

Across the border in Tijuana, authorities said a mudslide killed an unidentified 39-year-old woman and her 3-year-old child when it struck their house as they slept. The victims, both of whom died of asphyxiation, were identified as Maria Del Socorro Varga de Castaneda and her son, Cristian.

Tijuana authorities evacuated scores of families from their homes, and roads throughout the city of about 1 million have been severely flooded or blocked by walls of mud.

As stormy weather lingered in Southern California, clearing skies moved into the previously hard-hit northern part of the state. At the Sierra resort of Kirkwood, which had received 90 inches of snow in the storm, helicopters joined a search for two snowmobilers who had disappeared Saturday.

Authorities in Stockton recovered the body of a child who disappeared in the Calaveras River and sought three others, ages 7 to 9. The dead child’s name was withheld.

“Two of the children slipped into the river while playing and three others jumped in after them. One was able to get out and called for help,” Coast Guard Lt. James Wierzbicki said.

The succession of March storms followed months of what was one of the driest periods in the five-year drought that has plagued California. Water experts say the storms have probably stemmed the advent of even more stringent water rationing in the state, but in most areas have been insufficient to end rationing already in effect.

Both Los Angeles and San Diego received heavy new rains late Tuesday and early Wednesday, with Los Angeles Civic Center getting 0.84 of an inch in the 24 hours ending at 3 p.m., bringing its season total to 11.95 inches. San Diego, with 1.09 new inches, has a season total of 11.73 inches.

Dolores Taylor, senior hydrologist at the Ventura County Flood Control District, said more rain fell in Ventura this March, a total of 12.88 inches, than had ever been recorded there for the month.

Times staff writers Patrick McDonnell and Bernice Hirabayashi contributed from San Diego, Tina Daunt from Ventura, and Bill Billiter and David Reyes from Orange County.

THE MAKING OF A TORNADO

Recent storms have stirred up tornadoes and funnel clouds from Santa Barbara to San Diego, with the most serious twister touching down in Huntington Beach Tuesday night. Up to 50 homes were damaged, but no one was injured. Here is a look at how a twister is formed:

1. A low pressure system in the upper atmosphere moves over the Los Angeles Basin.

2. Temperatures in the upper atmosphere drop, making the atmosphere unstable and forming deep showers and thunderstorms.

3. Swirling winds around the low in the upper atmosphere help to get the showers and thunderstorms rotating.

4. The shape of the Los Angeles Basin is such that low winds are forced to flow in a “cyclonic” direction (from the south to the west) encouraging rotation to begin.

This is how the weather looked over the Southern California area Tuesday night. A low pressure area--called a comma cloud by meteorologists because its shape resembles that of the punctuation mark--moved over the Southland. Cold cumulous clouds in the upper atmosphere created the thunderstorm and spawned the tornado in Huntington Beach.