Storm over Merced and Mariposa knocks mud and rocks onto Highway 140

There were some reports of localized flooding in Merced County as a storm hung over the central San Joaquin Valley, but the most significant weather phenomenon reported Thursday was in the foothills.

Highway 140 in the El Portal area was obstructed briefly by rocks in the roadway but the U.S. Department of Transportation used plow trucks during the day to keep highways clear, according to the California Highway Patrol.

No highways were closed due to the storm on Thursday, confirmed Thomas Lawrence, a Caltrans spokesman.

The National Weather Service in Hanford issued a severe weather warning during the afternoon that ended about 2:30 p.m. for Merced County and Mariposa as the service tracked thunderstorms and winds greater than 30 miles per hour.

Most of Merced and Mariposa counties saw 2 inches of rain or more, according to meteorologist Dan Harty.

The service also warned that areas of Mariposa County scarred by last year's wildfires could be subject to flash flooding and mudslides. State and local officials were working proactively to keep roadways clear, according to CHP Officer Adrian Perez.

"We're bracing for the worst but hoping for the best," Perez said.

The northern part of Mariposa County and Sonora were getting the worst of the weather with hail reported in some areas, Perez said. Schools were dismissed early so students could get home before the storm was its worst.

Some county roads with one-lane bridges were closed in anticipation of rising waters, Perez said.

CHP was also responding to reports of trees down on Auberry Road north of Highway 168 and Highway 49 in the Oakhurst area.

Highway 59 was closed between Oakdale Road and Nevada Street due to flooding, the Merced-area CHP reported around 3:30 p.m. "Please do not attempt to drive through standing water as roads covered by water are prone to collapse," the Facebook post said. "There are currently several vehicles stuck in the area."

Many urban areas saw local flooding as well. "It's raining so hard in some areas that the drainage system just can't keep up," Harty said.

Thunderstorms continued late in the Planada area, but were expected to taper off by sundown, he said. The foothills can expect to see showers Friday, but most of the Valley is forecast to be dry.

The National Weather Service issued a "flash flood watch" in Mariposa until 8 p.m. Thursday for areas below 8,000 feet.

Merced County had no major flooding, according to county spokesman Mike North.

A number of minor-injury car crashes were reported Thursday on Highway 99, including a solo-vehicle rollover near Sultana Drive in Livingston.

This story was originally published March 22, 2018 at 8:53 AM with the headline "Storm over Merced and Mariposa knocks mud and rocks onto Highway 140."