Flash flood watches are in effect in the Northeast for some of the same areas hit by Ida

By Judson Jones, CNN Meteorologist

The first storms since Ida will move through the Northeast into Thursday, bringing the chance for severe weather and possible flash flooding.

Flood watches have been issued for over 12 million people just west of New York City, in New Jersey, Pennsylvania and New York state.

A flood watch means you should monitor upcoming forecasts and be prepared to take action should flash flood warnings be issued.

“This watch serves mainly to highlight the potential for rapid runoff of any heavy rain that falls given the very saturated soils from recent heavy rainfall events across the area,” the National Weather Service said Wednesday morning. “It will not take much rainfall to cause flash flooding of urban, flood-prone, and other low-lying areas.”

As of Wednesday evening, there were reports of trees down in Montgomery County, New York, and Chittenden County, Vermont, with some hail in northern Vermont.

The line of storms was expected to move through the New York City metro area late Wednesday, with heavier rain and gusts expected in some areas. There is a concern of localized flash flooding.

Normally, this line of forecast storms might not have made the threshold for issuing these watches. But, with the ground so heavily saturated, the bar for flooding has been lowered.

The ground is like a sponge, and when it is soaked through, it can’t hold much more water.

“Any measurable rainfall, especially amounts greater than 2 inches, will potentially aggravate ongoing flooding over the entire region,” the Weather Prediction Center said.

The center has issued a marginal risk — level 1 of 4 — for excessive rainfall and flash flooding spanning an area from northern Virginia to northwest Maine.

It has issued a slight risk — level 2 of 4 — stretching from extreme northeast Maryland to southern Vermont.

“There are also increasing signals for extremely isolated areas that could receive 3 to 5+ inches (especially along the Pennsylvania and New Jersey border) that may need a moderate risk area (level 3 of 4) given the severity of possible local flooding impacts,” the WPC said Wednesday morning. “However, this system is very progressive and pinpointing where is very difficult at this time.”

“The main period of concern is during the evening hours as a line moves through west to east,” the NWS said. “However, there may be some scattered storms that form ahead of the line this afternoon.”

Severe winds and tornadoes are also possible

There is a slight risk — level 2 of 5 — for severe storms from Virginia to Vermont.

It includes Washington, DC, Baltimore, Philadelphia and Paterson, New Jersey.

“A couple tornadoes seem probable along with strong gusts producing scattered damaging winds and isolated severe hail,” the Storm Prediction Center said.

A marginal risk — level 1 of 5 — for severe storms covers a more extensive area of the Northeast. It includes New York City, Virginia Beach, Virginia; and Charlotte and Raleigh in North Carolina.

Although the probability for severe storms is lower in these areas, there is still at least an isolated severe threat during the afternoon and evening.

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CNN meteorologist Gene Norman contributed to this report.