(CNN) — The Northeast is facing a flash flood threat this week from an unusually strong storm that could drop up to a month’s worth of rain in just a few days in parts of the region.
The soaking system will be spawned by a pocket of energy that’s firing up severe thunderstorms in parts of the Great Lakes and Ohio Valley on Monday. Powerful wind gusts that could knock out power and down trees are the primary threat in those regions, but isolated tornadoes are possible. One “extremely dangerous” tornado hit northeast Wisconsin Monday afternoon.
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On Tuesday, the energy will spin its way into the Northeast, where it will intensify and slow down dramatically. It’s expected to linger over parts of the region through at least Thursday.
The storm’s strength when it’s over central New York on Wednesday will be more on par with a system we’d expect to see in October, November or December — not late-July. Storms are usually weaker in summer than winter because the jet stream doesn’t have as much energy to intensify them.
At the same time, the system will tap into pipelines of Atlantic and Gulf moisture that have souped up to levels well above average for even midsummer’s humid reputation.
Those extreme opposites will clash and cause multiple rounds of heavy rain and thunderstorms to flourish over the Northeast.
The forecast
The New York Tri-state area to Philadelphia has the biggest risk of flooding rain on Tuesday and Tuesday night, but a localized threat covers most other parts of the Northeast.
A round of rainfall from eastern New York to Pennsylvania in the morning will likely be followed by additional bouts in the afternoon and evening. The heaviest storms could produce rainfall rates of an inch or more per hour.
Urban and poor drainage areas are most likely to have the biggest flooding concern, but it’s not certain whether this week’s flooding impacts will rise to a more serious level as it has multiple times across the United States this month, including in New York City on July 18.
Farther south, severe thunderstorms are a threat on Tuesday from around Washington, DC, to North Carolina. Wind damage is the primary concern from any storms that intensify.
The most expansive flash flood threat will shift a bit farther north on Wednesday into southern New England, including Boston and Hartford, but New York City will also remain at risk.
Downpours will likely be ongoing across this area as the day begins. Flash flooding could unfold as one or more narrow bands of heavy rain spread northeastward through the afternoon. New storms could form behind this area as well.
At least scattered flash flooding impacts are possible, especially in urban and poor drainage areas, the National Weather Service in Boston said. Travel delays are likely at airports and on roads throughout the region.
Pockets of heavy rainfall could persist in parts of the Northeast on Thursday, but it’s a little too soon to pinpoint any specific flooding concerns.
Much of the Northeast flood threat area will pick up 1 to 4 inches of rainfall through Thursday.
Higher amounts are possible in locations that are hit with the most rounds of rain, and in spots where bands of rain slow down or stall out for multiple hours. These spots would also have a higher chance of seeing more serious flooding impacts.
The storm will weaken and push out of the Northeast on Friday, but a few scattered showers and storms could still billow up over the region.
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