The combination of a deep fetch of moisture extending well out into the tropical and sub-tropical Atlantic, a series of jet stream disturbances lifting north and eastward up and through the Eastern United States and a stalled out frontal zone wavering north and south over the Mid-Atlantic and Southern New England will be the impetus for multiple rounds of wet weather in the coming days.
This signal has been on model guidance for over a week’s time but details as to exactly where the heaviest rain sets up remain unclear at this point – or rather, whether that heavy rain makes it into our neck of the woods or stays focused a bit further south is the main forecast question.
Note on the ECMWF Ensemble Mean (a blend of 51 weather models) heavy rainfall is expected over the next several days from south to north across just about the entire Mid-Atlantic, with a distinct axis of heavy rain running eastward, parallel to the South Coast of New England. That west to east axis of heavy precipitation is the result of the west to east frontal zone stalled out south of the area…and multiple waves of low pressure expected to ride along it.
Not surprisingly, guidance has been subtly shifting this boundary north and south with each model run for several days…in some cases allowing the boundary to shift into Southern New England and yielding an extremely wet period later Friday and throughout the weekend…while at other times keeping it further south, yielding a more showery outcome with the steadiest and heaviest rains remaining south of the area.
Right now, it is safe to expect at least some wet weather later this week and into the weekend but whether we see modest amounts of rain or a real heavy soaking won’t be known for another day or two.