Downpours to end much of Northeast's dry spell as flash floods return to Southeast
The stretch of dry and hot weather will be put on pause this week in the Northeast as disruptive thunderstorms drench the region on Wednesday. Meanwhile, tropical downpours will trigger flash floods in the Southeast.
Thunder boomed and rain poured throughout the Northeast on Aug. 13, leading to flash floods that stranded cars in some areas.
Downpours should break the current heat wave and dry spell in the Northeast and are poised to renew dangerous flash flooding in the Southeast, AccuWeather meteorologists warn.
Boston's last drenching rain was on Aug. 1 with 0.28 of an inch. New York's Central Park picked up 0.06 of an inch on Aug. 6. In some cases, the last rain that dampened the ground or produced puddles was in late July. Rainfall during the first 10 days of August usually ranges from 1 inch to 1.50 inches.
Multiple locations in central Pennsylvania, for example, were experiencing one of their driest starts to August on record. Through Aug. 12, Williamsport was the driest ever, while Harrisburg and Altoona were the second driest. State College was tied for second driest for the first 12 days of the month.
The lack of rain, plenty of sunshine, breezes, and days of low humidity have turned lawns brown, however. Unwatered gardens and crops are showing signs of stress. Water levels on some small streams are dropping despite what was a wet end to spring and the first part of summer.
Part of the same storm system responsible for flash flooding in the Midwest over the weekend will slowly drift eastward through Thursday. At the same time, some moisture will join in from the Gulf and the Atlantic.
At this time, the rain is unlikely to trigger flooding anywhere near the scope seen around Milwaukee. Rainfall in the Northeast is likely to average 0.25 to 0.50 of an inch, with a few spots picking up 1 to 1.50 inches.
A brief torrential downpour can reduce visibility and cause ponding on roads and highways. Where rain lasts more than a few minutes, some storm drains could briefly be overwhelmed.
Clouds paired with showers and thunderstorms will help to trim high temperatures in the region from midweek on, but the same moisture will result in muggier nights compared to prior days. More downpours will be possible in coastal areas of New England and much of the mid-Atlantic Thursday.
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Despite the likelihood of widespread showers and thunderstorms in the Northeast from Wednesday to Thursday, some areas may manage to avoid meaningful rainfall. The next chance of sporadic showers and thunderstorms will be over the weekend from a cold front dropping down out of eastern Canada.
As dry air advances later in the week, humidity levels and temperatures will be trimmed in the Northeast, especially over the interior and northern tier, where the heat has been the most extreme, relative to the historical average.
Flash flood risk is higher in Southeast states
In the Southeastern states, where humidity levels will be much higher and moisture more plentiful through Wednesday and into Thursday, the risk of flash flooding in urban areas and along small streams will be significantly higher, especially in areas that have received heavy rain over the past week.
As a weak area of low pressure treks across the Southeast on Wednesday, it will enhance the thunderstorm activity along its path. This weak low was being monitored for tropical development from Monday to Tuesday while over the northern Gulf, so it does have some tropical characteristics about it, mainly in the form of torrential downpours and gusty thunderstorms.
On Tuesday evening, the Chattanooga, Tennessee, area was deluged by heavy rain, which caused flash flooding.
Due to repeated storms on Wednesday, there will be a heightened risk of flash flooding, ranging from northern Georgia and eastern Tennessee to upstate South Carolina, western and central North Carolina, and south-central Virginia. Should several inches of rain pour down in a couple of hours or less, the situation could escalate to a life-threatening situation.
Near, south, and east of the flash flood risk zone will be gusty to locally severe thunderstorms over portions of the Carolinas and southern Virginia on Wednesday.
Looking ahead, those heading to the beaches for a late-summer getaway this weekend to next week should monitor the track and intensity of Tropical Storm Erin. At the very least, Erin will cause a significant uptick in seas and surf along the U.S. Atlantic coast with strong and frequent rip currents.
Watching South Texas for a heavy rain event
Another area being watched for torrential downpours and flash flooding is in South Texas for this weekend, as a surge of tropical moisture moves northwestward from the Gulf. It is possible this moisture quickly evolves into a tropical depression or storm late this week.
The area of concern includes part of the Rio Grande Valley and the Texas Hill Country. Deadly flash flooding crushed the hills northwest of San Antonio around the Independence Day holiday.
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