Widespread downpours to ease drought in eastern US, elevate flash flood risk
Rainfall will bring drought relief to much of the Eastern U.S., but downpours may cause flash flooding, slick travel, and localized hazards through the end of the week.
The Mississippi River is responsible for transporting 55% of all U.S. soybean exports. When dry weather leads to low water levels, it can significantly disrupt barge traffic and impact the delivery of these goods to market.
Rain will expand into more drought-affected areas in the eastern United States through the end of this week.
There are dangers associated with the rain and locally severe thunderstorms, and they go beyond slick highways. Rain may fall too quickly for some storm drains and small streams to handle, potentially leading to flash flooding.
Prior to the break in the weather pattern this week, many areas in the eastern U.S. recently experienced one of the driest ends to summer on record. Fall officially began Monday.
Most of the rain will be beneficial in terms of watering lawns, forests and late-season crops. A lack of soaking rain has left many lawns brown and dormant, and accelerated the fall foliage. Instead of a lasting display of fall color, the rapid leaf change has caused some drought-stressed trees to drop their leaves early.
Small streams and secondary rivers have dried up or are down to a trickle, and some of the major rivers are running low. Portions of the lower Ohio River and the middle portion of the Mississippi River are at the minimum threshold for normal navigation.
One of the most common issues when it first rains after a long dry stretch is the combination of water and oil buildup on area roads and highways. Until it rains hard enough to wash away the oil residues, roads may become especially slick, contributing to accidents, especially at intersections, highway ramps and in emergency braking situations.
Much of the zone from Kansas and Oklahoma to Kentucky and Tennessee has received 0.50 of an inch to 2 inches of rain, with locally higher amounts, which in many areas has been readily absorbed by the ground. A few locations have received 50 to 100 percent more rainfall than adjacent areas, or much of the rain fell in an hour's time. This has led to quick runoff, ponding on some roads, and isolated incidents of flash flooding.
This map shows accumulated rainfall from Noon Monday to Noon Wednesday, EDT.
As the showers and thunderstorms advance slowly eastward, additional rainfall—both beneficial and potentially problematic—will extend across the Appalachians and onto the Atlantic Coastal Plain and the northeast Gulf region into the end of the week.
As a storm moving along a press of cooler and drier air travels from the Ohio Valley to the St. Lawrence Valley from Wednesday to Thursday night, a broad area of drenching rain and locally gusty thunderstorms will affect the northeastern quarter of the nation.
As the cold front associated with that storm presses on to much of the Atlantic Seaboard on Thursday afternoon and evening, gusty and potentially severe thunderstorms are expected to unfold.
Travel delays are possible as the storms traverse the Interstate 85 and 95 corridors, including the major hubs of Boston, New York City, Philadelphia, Washington, D.C., Charlotte, and Atlanta.
As some dry air pushes across the interior Northeast Friday, showers and thunderstorms will persist from Florida to Georgia, Alabama and the Carolinas.
Another round of gusty downpours may affect coastal areas of the Northeast as well.
From later this weekend to the first part of next week, the tropical Atlantic could dictate the extent of rain along a portion of the Atlantic Coast. Should a tropical storm or hurricane (Imelda) spin toward the coast, rain and wind and surf could become very problematic.
As the risk of heavy rain lingers in the Southeast, a long-duration dry weather pattern will return to the Central states and later in the Northeast.
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