A storm that passes south and east of Long Island is the classic setup for snow because it allows the cold air that's in place to stay in place.

This is something that is not common. Especially coming off one of the driest months of the year. It's a remarkable pattern in terms of heavy rainfall without the remnants of a tropical system or hurricane. It's dramatic after a long period of dry weather being dramatically broken by long periods of prolonged rain. This is usually a quiet month.