As an upper-level trough tracks east while a surface low pressure moves northeast from the Gulf Coast, the development of rain and even some thunderstorms will begin to affect the Northeast on Thursday. This will continue into Friday as all of the moisture tracks eastward.
Typically, surface low pressures will result in both a warm front and a cold front. A warm frontal boundary will span across the eastern Great Lakes and into northern New England, bringing light rain showers to much of the region on Thursday. Back to the south and west, there will be a cold front across the Ohio River Valley. Between these two boundaries — south of the warm front and east of the cold front — is what we call the warm sector. This area of relatively warmer, moist air that is forecast to gradually stabilize through tonight, leading to the small risk for a few severe storms beginning this evening, especially across central Pennsylvania into central New York. The main risk associated with these storms will be damaging winds, but a spin-up tornado cannot be ruled out.
Meanwhile to the south, severe storms will also be possible across parts of the Gulf Coast states and the Southeast. The best risk for the intense storms will be in southern Alabama and the western Florida Panhandle. Not only will damaging winds and small hail be possible as the widespread line of thunderstorms moves east through the region, but a few tornadoes may also be expected. Unlike other severe weather setups, this particular setup may feature severe weather at any time of the day, even in the morning when the risk is typically lower than in the afternoon and evening.