Thunderstorms trigger flash flood warnings in 4 North Jersey counties, warnings for entire state

A flash flood warning has been issued in four counties in northern New Jersey with the rest of the state under a flash flood watch as torrential rains bring rising rivers that can quickly overwhelm their banks and flood nearby roads, according to the National Weather Service.

Morris, Somerset, Sussex, and Warren counties were all upgraded to a warning after 1 to 2 inches of rain fell this afternoon. Now, an additional 1 to 3 inches are expected in those counties with flash flooding expected to start and be ongoing in some areas, according to the National Weather Service.

Flash floods were likely in Morristown, Newton, Dover, Madison, Hopatcong, East Hanover, Lincoln Park, Kinnelon, Hackettstown, Boonton, Butler, and Wharton, the weather service said. Already, some Denville roads were detoured because of flooding.

The warning expires at 9 p.m.

Early forecasts had called for thunderstorms to dump up to 2 inches of rain an hour with wind speeds that could be as high as 60 miles per hour, according to the weather service. However, winds did not seem to materialize during the afternoon and were not included in the weather service's latest warning.

The rainfall will be particularly bad because of how slow-moving the storms will be, giving them a chance to dump enough water on the surface and cause flooding, said weather service meteorologist Bryan Ramsey.

Flooding will be likely in areas with poor drainage and in urban areas. “Excessive run-off may result in flashier small streams, rivers, and creeks rising out of their banks,” the weather service said.

Ramsey said the flood watch goes into effect at 2 p.m., but the worst of it could start after 6 p.m. According to the weather service, the flood watch will remain in effect through the evening.

“You should monitor later forecasts and be alert for possible flood warnings,” the National Weather Service said. “Those living in areas prone to flooding should be prepared to take action should flooding develop.”

This article originally appeared on NorthJersey.com: North Jersey could be hit by floods, damaging winds