Thunderstorms to bring excessive rainfall, keeping flood threat high in Northeast
AccuWeather meteorologists are warning that more incidents of flash flooding can occur in parts of the Northeast this week as disturbances pivot from the Midwest.
As has been the case throughout the month of July, and most recently in the suburbs of Philadelphia where at least 6 were killed during a flash flooding event, rainfall of 1-2 inches per hour can occur into Tuesday evening due to an eruption of heavy to locally severe thunderstorms.
Extreme flooding events have occurred over the past couple of weeks in parts of eastern New York and New England. "In these areas, excessive rain occurred over several hours and initiated flash flooding on a regional basis," AccuWeather Senior Meteorologist Alex Sosnowski said.
Weather systems tend to move slowly during July, and very warm and humid conditions are a given during the summertime. With the hottest weather of the year possible this week in the Northeast, this combination can cause big trouble - especially in areas that are already waterlogged.
More flooding trouble is possible early this week, forecasters say.
"Due to the amount of moisture in the atmosphere and weak steering winds, any shower or thunderstorm has the potential to produce localized flooding downpours into Tuesday evening," AccuWeather Senior Meteorologist Dan Pydnowski said.
Into Tuesday evening, heavy storms are expected to set up from northern Virginia northward into the New York City area, the lower part of the Hudson Valley and southern New England. Although many locations in this region will not experience excessive rain from thunderstorms, there will be a high risk of flash flooding in locations where storms do set up.
AccuWeather meteorologists warn that where slow-moving, heavy storms set up, rainfall totals of 1-2 inches with highly-localized amounts of 3 inches could lead to a risk of flash flooding, especially in low-lying and poor drainage areas.
People in or traveling through the metro areas of New York City, Philadelphia, Baltimore and Boston will be at risk for heavy thunderstorms into Tuesday evening.
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"Because of the vast amount of urbanization in these locations, the storms may flood streets, highways and underpasses," Sosnowski said. "This alone can lead to major travel disruptions. And, as locally severe storms pass nearby the major airports, ground stops and flight delays are likely."
The bulk of the drenching storms are likely through 9 p.m., but there will be some exceptions, Sosnowski added.
There were storms that rolled through central Pennsylvania first thing Tuesday morning. Some downpours with thunder and lightning are likely to linger well into the night along the immediate Atlantic coast.
Forecasters say residents planning to spend time outdoors in the areas at risk into Tuesday evening should closely monitor the weather forecast and be alert for changing conditions.
Even in areas where flooding does not unfold there is the likelihood of sudden downpours, lightning strikes and strong wind gusts. Where the soil is saturated, trees may topple more easily compared to when the ground is dry.
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Any areas that were recently inundated during heavy rain in the past week will be at risk for flash flooding. Any severe thunderstorm in this setup can also produce hail and localized damaging wind gusts of 55-65 mph. An AccuWeather Local StormMax™ of 75 mph is possible in some localized areas.
Thunderstorms on Monday produced enough rain in Albany, New York, to officially make this month the wettest July in more than 200 years.
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Calmer conditions are likely on Wednesday. However, a new round of gusty storms is expected in portions of the Northeast on Thursday. In addition to a threat for localized flooding, damaging winds and hail can occur in stronger storms.
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