Parts of the mid-Atlantic flooded by Tropical Storm Isaias on August 4 may re-live a similar situation today.
Thunderstorms have already produced up to two inches of rainfall in portions of the Delmarva Peninsula this morning, prompting the National Weather Service (NWS) to issue a flash flood warning.
NWS forecasters are calling for several more rounds of showers and thunderstorms across the mid-Atlantic through tonight. This could lead to additional areas of localized flash flooding, along with potential closures of roads and highway ramps along the Interstate 81 and 95 corridors.
Two days ago, places like Allentown and Philadelphia, Pennsylvania, as well as Wilmington, Delaware, had daily record rainfall between 4 and 5 inches. Daily record rainfall was also set in Washington, D.C. at Ronald Reagan (ICAO code: DCA) and Dulles (ICAO code: IAD) airports.
Because more soaking rains will hit areas where the ground is still saturated from Isaias, this increases the odds of rivers, creeks and streams rising rapidly, leading to flash flooding. Storms could drop several more inches of rainfall today.
The NWS has issued a flash flood watch stretching from the Philadelphia metropolitan area to the Delmarva Peninsula; Washington, D.C.; Baltimore, Maryland; as well as Charlottesville and Harrisonburg, Virginia.
The key high-volume trucking markets of Harrisburg and Allentown, Pennsylvania, in addition to Elizabeth, New Jersey, are on the bubble as far as flash flooding potential. They lie just outside the watch area, and they rank third, sixth and seventh, respectively, in terms of how much outbound freight they have that is up for grabs. The FreightWaves SONAR Outbound Tender Volume Index (OTVI) measures this, and the leading markets are located in the upper left-hand portion of the chart below.
Besides occasional torrential rainfall and reduced visibility, storms today may also produce dangerous wind gusts and large hail at times.