An upper-level low broke off from the flow aloft earlier this week, and that same low was being monitored by the National Hurricane Center for Tropical development as early as Wednesday morning. Now a subtropical storm named Josephine has formed.
Josephine formed Wednesday afternoon as a subtropical storm. That means this storm is not forming and churning because of warm sea surface temperatures. Subtropical means this storm is using warm water, but it also has cold air aloft that it's using to grow and increase in intensity. A way of noticing a subtropical storm is no well-defined eyewall.

Wave heights between 10-20 feet will be possible at times, making for dangerous conditions.
High winds with Josephine will wear down many beaches along the eastern seaboard. What's of most concern are the beaches in North Carolina, which stick out farthest, and places like Virginia, which will have to endure days of breezy winds agitating the seas. Waves of 10-15 feet can be expected, which will help push a few feet of seawater onshore into normally dry stretches of the coast.

Wind gusts could reach 40-50 mph at times throughout the week as well. The questions about rainfall hinge on the location of the low. At this time, only areas along the coast could get a few showers, with the best chance looking like Wednesday.
More updates on this evolving setup will be coming up all day and night on WeatherNation.