This temperature gradient creates instability, fueling a low-pressure center that intensifies as it moves toward New England and the Canadian Maritimes.
Some nor'easters undergo "bombogenesis" (becoming a " bomb cyclone "), where pressure drops at least 24 millibars in 24 hours, leading to rapid intensification. Core Characteristics What Is a Nor'easter? | NESDIS - NOAA
Cold, dry arctic air from Canada pushes south and meets warm, moist air from the Gulf Stream over the Atlantic Ocean.
Nor'easters thrive on the extreme temperature contrast between two air masses.