Almost 50M under flood watch as major thunderstorms bring 12INCH rainfall and 55mph gusts batter West Coast - with some parts of US expecting tornadoes

A powerful Easter storm system delivered flash flood warnings to much of Los Angeles County and heavy rain across the rest of California and into the nation's heartland, impacting some 50million Americans.

Models of the forecast show a widespread severe weather event will hit the middle of the county on Monday before making its way east toward Tennessee and Ohio.

The thunderstorms may wind up delivering dangerously strong wind gusts, as well as lightning strikes and tornadoes.

FOX Weather Meteorologist Jane Minar said: 'What starts in the West must eventually come East. All of that energy, as it shifts through the weekend over the Four Corners, gets a second life as it develops over the central US.'

NOAA's Storm Prediction Center said that on Monday, states like Oklahoma could experience 2-inch wide hailstones.

Some of the tornadoes, warns the organization, may take place overnight on Monday. Nocturnal tornadoes are more than twice as likely to result in fatalities.

In the northern-central Plains, the storm system will likely deposit snow and freezing rain on Sunday night. Those cold-weather storm qualities could stretch as far north as the Upper Midwest and Great Lakes region on Monday.

Later into the week, showers and thunderstorms will blanket Tennessee and the Ohio Valley, stretching into northern Mississippi and Alabama.

Louisville, Kentucky is also in the storm's path.

Though the threat level will not be as high as on Monday, those areas are still being advised to prepare for all modes of severe weather.

Minar said: 'The key messaging here is that as we follow what happens with the rain over the weekend in the West, don’t lose sight of the start of the new week, the start of the new month.'

Weather alerts, she said, are a necessity in April - a month that typically comes with an increase in severe weather as air masses clash in the East.

California is finishing up the second very snowy winter in a row.

Over Easter weekend, the state's mountain region received a significant amount of snow with the weather pattern extending East into the Rockies in Colorado and Wyoming, where more than 12 inches of snow may fall.

The Southwest is under high wind alert, with mostly all of Arizona under an advisory that winds could reach speeds of up to 55mph. 

The severe weather that will continue into the midweek will also extend as far South as Texas and as far Northeast as Baltimore, Maryland - where crews tasked with investigating and cleaning up the Francis Scott Key bridge collapse will need to pay careful attention to the weather blowing in from the West.