Heavy Rain and Flash Flooding Threaten Mid-Atlantic and Northeast

New York Times

5 days ago

Widespread storms are expected to bring periods of intense rainfall to parts of the northern Mid-Atlantic and the Northeast on Thursday, as forecasters said that up to eight inches of rain could fall in some areas and raise the risk of a 'potentially significant flash flooding event.'
The weather conditions leading to the bouts of heavy rain involve a cold front moving across the region. Richard Bann, a meteorologist at the Weather Prediction Center, said that the front was interacting with unusually warm, humid and unstable air for this time of year.
'That's going to allow the storms to become stronger,' he said. 'With some very intense rainfall rates, upward of two inches per hour.'
The Weather Prediction Center issued a Level 3 out of 4 risk for excessive rainfall from northeastern Virginia to New Jersey, including Washington, D.C., Baltimore and Philadelphia, through Friday. A wider area, from eastern Virginia to Connecticut, including Richmond and New York City, was under a Level 2 out of 4 risk. Flood watches were also issued across much of the region.
The center highlighted two main areas of concern when storms begin to develop in the region on Thursday afternoon.
From northeast Pennsylvania through southern New England, rainfall of up to 1.5 inches per hour was expected. Forecasters said locally significant flash flooding was likely, particularly for areas close to the Poconos and the higher elevations of southern New England.
Farther south, the storms were forecast to be more intense. From northern New Jersey to Northern Virginia, up to three inches of rain per hour was expected, especially in the Washington D.C., and Baltimore areas, extending into southern New Jersey. The center said that some places were expected to get over five inches of rain.
Because the affected area includes major urban centers, including the I-95 corridor, Mr. Bann said that flash flooding could lead to serious disruptions, especially since repeated storms over the same locations were expected.
'It's also been very wet in some of these places, like Washington D.C.,' he said. 'The ground already has water in it, so any additional water on top of it is going to be more likely to run off as well.'
Once the front passes through, the outlook is looking drier and cooler from Friday.
'There might be some lingering rain along the coast,' Mr. Bann said. 'But the heavier activity will have gone.'