For all 21 counties in New Jersey, through Wednesday afternoon and evening, a severe thunderstorm watch has been issued, with the possibility for heavy rain, hail, and wind gusts up to 70 mph, the National Weather Service said.  

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According to forecasters, storms are predicted to push from west to east and begin impacting northwestern New Jersey as early as 11 am.

Storms will be a threat for much of the afternoon and evening with the worst of the weather moving out to sea by about 7 pm. The heaviest of the rain is likely to fall along and east of the Interstate 95 corridor, according to the weather service.

Storms are likely to concentrate east of Washington, with the biggest danger of severe weather in New Jersey and southern New York. However, a few strong storms in the District, particularly in our eastern suburbs, are probable.

Storms will approach from the northwest, which is a bit rare. They're being fuelled by a westerly-southwesterly air mass that's unstable and humid. A trough or dip in the jet stream is approaching in the high atmosphere, enhancing the dynamic uplift over the Mid-Atlantic.

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Mid-level winds are increasing within the trough, causing wind shear. In storm cells, wind shear tilts the updraft away from the downdraft, preventing the two from colliding and enhancing storm intensity.

"A moist and unstable air mass will exist near the front, with several severe storms expected by early afternoon," the NWS Storm Prediction Center said Wednesday morning, according to CT Post.

Although a severe thunderstorm watch is not as serious as a warning, it does indicate that the circumstances are favourable for very intense storms with destructive winds, big hail, and frequent lightning.