Atmospheric river to trigger central US flooding that may become life-threatening, historic
Up to 4 month’s worth of rain may fall in less than a week across part of the central United States, threatening major flooding and endangering lives and property.
Extreme storm chaser Aaron Jayjack recaps what he witnessed while tracking tornadoes and flooding caused by the storms across the central U.S. on April 2.
A firehose of moisture is forecast to produce repeating thunderstorms with torrential downpours over the middle of the United States through much of this weekend. More than a foot of rain may pour down from portions of Arkansas to Kentucky and Ohio, likely triggering rapid, major and historic flooding, AccuWeather meteorologists warn.
More than 46 million people will be affected by rounds of intense rainfall over the central U.S. Of this, at least 13 million will be within a high- to extreme-flood risk zone. Within these higher-risk areas, there is the potential for catastrophic flooding in some communities.
Heavy rain and subsequent flooding problems began on Wednesday night and will escalate daily from there.
Except for a stretch of days in February, storm systems have moved steadily along. However, that slow-moving storm in February unleashed many inches of rain on portions of Kentucky, West Virginia, Tennessee, Indiana and Ohio and resulted in major flooding and significant loss of life. The upcoming rainfall could be more than double that from February and poses that much more of a threat to lives and property.
The downpours' normal west-to-east or northwest-to-southeast path will be blocked by a building zone of high pressure over the Southeast states, which has evolved into a heat dome.
The setup caused a conveyor belt of moisture to form Wednesday night, which will continue into Saturday night, bringing many hours of heavy rain over multiple days from the Ozarks in Arkansas to the middle portion of the Mississippi Valley to much of the Ohio Valley.
"That moisture plume, known as an atmospheric river, will be tropical in nature and originate from the Caribbean," AccuWeather Senior Storm Warning Meteorologist William Clark said, "Tropical moisture raises the risk of excessive rainfall."
AccuWeather’s Leslie Hudson provided a live report from Memphis, Tennessee, concerning the likelihood for life-threatening flooding that could impact over 13 million people across the central U.S.
For those not as familiar with an atmospheric river, this will behave like a tropical storm moving slowly across the area. However, with multiple rounds forecast, it may be more like three or four tropical storms passing over the same region, with each unloading copious amounts of rain.
There is the potential for up to four months' worth of rain to fall in five days along portions of a 1,000-mile-long swath. Small streams and drainage systems in urban areas will not be able to handle the surge of rainfall. In extreme cases, rainfall rates of up to a few inches per hour can occur, which can lead to rapid flash flooding.
"Should the amount of rain occur that we anticipate over the middle of the nation, it would exceed the 500 to 1,000-year average," Clark said. "Truly, the potential is there for a historic flash flooding event."
People living along or traveling on roads near small streams in hilly terrain should be especially vigilant for rapidly rising water that can sweep vehicles and homes away.
As that surge of water works into the progressively larger rivers in the region, AccuWeather meteorologists are expecting flooding in unprotected areas. The major rivers most likely to have significant water level rises include the Ohio, Miami, Scioto, Wabash, White, St. Francis, Kentucky and Tennessee.
A surge is also likely on the lower portion of the Mississippi River as the Ohio contributes more water to the main stem than the upper portion of the Mississippi. In addition to flooding, the high, fast-moving water could affect tug and barge operations as April progresses, as it can take several weeks for the surge to cycle through to New Orleans.
Motorists who utilize secondary roads in the heavy rain zone should be prepared to seek alternative routes to get to their destination. Property owners should be prepared to take preventative action with the risk of evacuations in some communities as waters rise.
A word about river gauge forecasts
Most of NOAA's river gauge forecasts in the Ohio and mid-Mississippi basins did not predict any flooding for the upcoming event on Tuesday but has since jumped to major flooding at many sites as of early Friday morning.
AccuWeather meteorologists are expecting major flooding in the Ohio Valley basin and significant rises in the portion of the Mississippi River from the Ohio River confluence south in the coming days and weeks. Secondary rivers in the region may experience major to near-record flooding where each round of heavy rain overlaps. Even in areas that miss some of the rounds, there is still likely to be moderate to major river flooding.
Local, state, and highway department officials are encouraged to take preventative measures and prepare for a major flooding event. Some roads and bridges may be washed away or underwater, and significant damage to infrastructure is possible in some communities.
Dangerous severe thunderstorms to continue
The same setup will lead to multiple days of severe thunderstorms in the Central states.
Additional rounds of severe storms and tornadoes will be in store for a portion of the Mississippi and Ohio valleys into the weekend. Some communities could be under both a tornado warning and a flash flood warning at the same time.
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