Get ready: Powerful rainstorms could flood Yosemite, create trouble in Valley

Yosemite Valley could be flooded by storms expected to hit the central San Joaquin Valley and Sierra Nevada on Friday and Saturday.

Meteorologists with the National Weather Service in Hanford are anticipating the Merced River to rise above the Pohono Bridge in Yosemite Valley.

If that happens, park spokesman Scott Gediman said Yosemite Valley roads and campgrounds could be closed. Officials are still monitoring the weather and won't likely have a decision about potential closures until Thursday or Friday.

The Merced River flows under the Pohono Bridge on Jan. 8, 2017 in Yosemite National Park. SILVIA FLORES The Fresno Bee

The latest estimates on Wednesday morning put the Merced River's peak flood stage as high as 15.8 feet in Yosemite Valley, said Brian Ochs, a meteorologist with the National Weather Service in Hanford.

In Yosemite, if the flood stage reaches 10 feet, that could flood some campgrounds, said meteorologist Carlos Molina with the National Weather Service in Hanford. At 12.5 feet, water could reach roads. It would have to reach around 20 feet for building damage to occur, he said.

In addition to the Merced, the weather service said high runoff could cause sharp rises in the San Joaquin and Kings rivers.

The warm, subtropical storm from the Pacific is expected to hit the Valley and Sierra on Friday, with the heaviest precipitation falling overnight into Saturday morning.

Snow is expected to fall in the high Sierra, between 9,000 and 10,000 feet in elevation.

A flood watch is in effect in the Sierra foothills from Fresno County to Mariposa County, and the southern Sierra from Yosemite to Sequoia & Kings Canyon national parks.

In the Valley, the heaviest rainfall should be in the north, with Merced getting as much as an inch and a half over the two-day storm, with most areas in the south Valley getting less than an inch, Ochs said. Yosemite Valley could get between 3 and 4 inches of rain.

But the NWS issued this warning: " Residents should keep in mind that areas that flooded in the last heavy rain event could very easily flood again." Among the places hardest hit in the last storm was the town of Mariposa.

The rainfall is courtesy of an "atmospheric river," a band of precipitation that originates near Hawaii and stretches across the Pacific to California.

Rain totals in Fresno this year are just below normal. Fresno has received 5.68 inches of rain since Jan. 1. The average total for this time of the year is 6.33 inches, Molina said.

Carmen George: 559-441-6386, @CarmenGeorge