Its a series of 3 areas of Low Pressure. 2 upper level lows and a surface low. There is a low area of pressure stalled off Europe due to the blocking high over middle of Europe. The low that may produce us a 2-3ft medium period swell is the upper level low moving up into Greenland right now. There is an Arctic area of high pressure that will force that upper level low back down and will combine with the surface low heading out to sea tomorrow. This upper level low than will be come a cut off low. It will be blocked in by the stalled low off Europe. As this is happening the Arctic high will push the low down and will hover out our way on friday than move off to into Europe as the Area of high pressure pulls further out to sea. This event should not make much if any. Looking out into the long range there maybe a NE swell for people north of Cape Cod on Monday, Tuesday (7,8 of May) The best way to think of something like this is gears. You have one big gear turning clock wise above to other gears moving counter clock wise below it.
500mb Map. Thats wind you see not swell. Hope this helps.
http://i50.tinypic.com/241jp1w.jpg