By AccuWeather senior meteorologist
Published Feb. 22, 2022 11:54 AM EST | Updated Feb. 22, 2022 6:51 PM EST
A pair of cross-country winter storms forecast to deliver snow and icy conditions across the central and eastern United States this week will also unload multiple rounds of heavy rain and significantly increase the risk of flooding in portions of the Ohio, Tennessee and Mississippi valleys, AccuWeather meteorologists warn.
National Weather Service flood watches, warnings and advisories were in effect for more than a dozen states as of Tuesday morning as the first of two storms was spreading rain across portions of the central and eastern U.S.
"A general 2-4 inches of rain is forecast to fall from Louisiana to part of southwestern Pennsylvania during the first storm that will finish up at midweek," AccuWeather Senior Meteorologist Adam Douty said. An AccuWeather Local StormMax™ of 6 inches may occur with this storm alone.
While rainfall of this magnitude is certainly heavy enough to lead to minor problems from street flooding and high water along small streams, it is not typically heavy enough by itself to cause more serious widespread flooding.
However, the situation is different in this case. The rain is coming after a storm dropped 1-4 inches of rain late last week. Low evaporation rates and runoff from melting snow in some areas have already pushed some streams and rivers out of their banks this past weekend in portions of Ohio, Indiana, Illinois, Pennsylvania, Kentucky and New York.
To make matters worse, a second storm will bring another dose of rain from Thursday to Friday and some of that rain will drench areas hit by the first storm and those that picked up rain last week. The second storm could bring another 2-4 inches of rain with locally higher amounts.
"The combined rainfall from both storms this week may range between 4 and 8 inches and could approach 10 inches in localized areas," Douty said.
That magnitude of rainfall over a three- to four-day stretch and on top of what fell from last week can easily trigger major flooding along small streams and in low-lying areas and lead to significant flooding along unprotected areas of some of the larger rivers in the region.
River level gauges at multiple points along the Ohio River in Kentucky, Indiana and Ohio were already at the minor flood stage on Wednesday, with some expected to reach the moderate flood stage later this week. Minor flooding is forecast by National Weather Service hydrologists along portions of the Kentucky River.
As rain pours down from the first storm and more is added by the second storm later this week, small stream and river levels could trend higher than currently forecast as more information is processed by hydrologic computer algorithms.
The greatest risk of flooding, ranging from urban areas to small streams and some of the larger rivers, will extend from northern Louisiana to southwestern Pennsylvania, an area that includes much of Arkansas, Kentucky, Tennessee and West Virginia. Other areas at risk include the northern portions of Mississippi and Alabama, southeastern Ohio, the southern portions of Illinois and Indiana and the western portions of Virginia and North Carolina.
Some of the major metro areas forecast to receive heavy rain from both storms this week include Nashville, Tennessee; Paducah, Kentucky; Little Rock, Arkansas; and Charleston, West Virginia. Some of these cities also received at least a thorough soaking from last week's storm. Nashville received a little over 2 inches of rain from the storm on Feb. 17, and more than 3 inches fell on Paducah from the same storm last week.
Water levels along small streams and in city streets could rise almost immediately during downpours, but rises along the larger rivers may take several days. On some waterways, dam mitigation may absorb some of the high water and limit problems downstream.
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In northern parts of northern New York, Vermont and New Hampshire, most of the flooding risk will stem from the first storm and ongoing runoff from last week's storm. As colder air presses in and heavy snow falls in this area and in northern portions of the Ohio Valley from the second storm, runoff should ease later this week, and stream and some river levels should stabilize.
A third storm may slice across portions of the Interstate 10 and 20 corridors in the southern U.S. this weekend, but the intensity of the rain is not likely to significantly aggravate flooding, and much of that rain is forecast to fall south of the hardest-hit rainfall zones from this week.
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