California communities bracing for heavy flooding as record high temperatures melt record amounts of snow

Communities in California are bracing for substantial flooding as near-record high temperatures threaten to melt record amounts of heavy snowpack.

Surface levels in bodies of water all over California are the highest they have been in decades since the start of the mega drought due to several rounds of atmospheric rivers that walloped the West Coast during the wet season.

The influx of rainfall has already saturated reservoirs and rivers, but a rampant rise in temperatures will quickly melt the incredible amount of snowpack that accumulated along the Sierra Nevada mountain range.

As many of the reservoirs are at capacity, the melting will have no where to go, experts say.

There is 221% more snowpack than average in some areas in California, according to the state's Department of Water Resources. The National Weather Service has forecast spring inflow to be 90% of the average in several waterways in California.

In the San Joaquin Valley, heavy thawing is expected to start Wednesday and will rapidly increase over the next seven to 10 days, Daniel Swain, a climate scientist at the University of California, Los Angeles, said Monday during the "office hours" session he streams on YouTube.

Several rivers are already at high surface levels and will likely exceed the flood stage this week, Swain said. There is particular concern for the level of inundation in the Tulare Lake Basin, which is already overflowing.

"There problem is, again, there's no where else for this water to go in the Tulare Lake Basin," Swain said. "It's just going to fill up like a bathtub.

Days before the substantial warming began on Wednesday. thousands of acres of farmland in the San Joaquin Valley were under several feet of water, with farmers racing to install new levees.

"The big melt is here," Swain said.

By Friday, temperatures are expected to reach record highs from California to Washington, with temperatures near Sacramento reaching 92 degrees and 105 degrees in Palm Springs by the start of the weekend. The National Weather Service has issued a flood watch the Sierra Nevada mountains in California and Nevada from Thursday into Monday in anticipation of the rapid melting.

As the heat wave continues, temperatures are expected to stay warm even at night.

Most of Yosemite Valley, a glacial valley in Yosemite National Park along the western slope of the Sierra Nevada mountains, will be closed due to forecasts for flooding starting Friday at 10 p.m. to May 3 -- possibly longer depending on the severity of the floods, the park announced on Twitter.

A cooldown is expected in early to mid-May, so there may not be a sustained period of above average temperatures, Swain said. However, once the heat is ignited this week, the region will continue to head toward rising temperatures through the summer, he added.

Earlier this month, the Department of Water Resources advised those living in snow melt areas to take steps to prepare for heavy flooding.

"Be aware of your flood risks, know where you're headed, know where your house or your business sits within or around potential for flooding," DWR officials said.