To start I want to say, this will not be the average 1 - 3 day forecast you will typically hear in late January, so lets get started. There is a large area of low pressure moving across the eastern plains, the midwest, and the eastern portions of the southeast currently. This system is full of heavy rain and severe thunderstorms, with some lighter snow on the back side because trailing this area of wet weather is a cold front that is in part helping trigger these thunderstorms. This system will move east across the country and effect the Ohio Valley, the southern portions of the northeast, the middle Atlantic, and the majority of the southeast except central and southern Florida. This system will be full of heavy rain and severe thunderstorms caused by the warm air and the instability of the atmosphere. Here is a forecast map of the setup for tomorrow for the northeast United States.
There area's in red have a 50% at seeing severe thunderstorms containing damaging winds from straight line winds. Also possibly some flooding. In orange there is a good chance for mainly heavy rain with some embedded strong storms. Tomorrow night there could be some light to moderate snows from Wisconsin to northern Pennsylvania. Here is a map of travel delays expected across the northeastern United States tomorrow.