5:15 AM

The dominant influence on the forecast area over the next several days will be the building western Atlantic ridge which will bring several different possibly impacts to the forecast area.  However, a few weak disturbances along the coast may still be able to bring some precipitation to the forecast area.

The overall 500 MB pattern over much of the United States shows a strong trough continuing to establish itself over the Rockies and a building ridge from the Mississippi Valley into the western Atlantic.  However, note the small “kinks” in the height fields over the Great Lakes, New England, and the coastal waters.  These “kinks” are actually weak disturbances racing from west to east through the northern portion of this upper level ridge, which happens to be right over the forecast area.  These disturbances are even more visible at 850 MB  where a defined weakness along the Mid Atlantic coast can be observed.

This weakness is a mid level coastal front born out of the differential heating between the land mass and the AtlanticOcean.  Naturally, high pressure at most levels of the atmosphere will keep much of the region dry through this weekend and into the start of next week, however the presence of the upper level disturbance and this weakness at 850 MB will keep the threat of isolated to scattered showers in the forecast into early next week.

The building western Atlantic ridge also will have additional consequences besides the threat of a few isolated showers.  For one, the persistent southwesterly upper and mid level flow will bring 850 MB temperatures over 15°C into the forecast area, which will support high temperatures in the upper 80′s to lower 90′s for several days for highs.  Also a significant increase in humidity can be expected as well.  However, the most intriguing influence may be the steering currents for the two tropical disturbances that will be approaching the Caribbean and Bahamas by the early portion of next week.  A trough will be established over the Great Lakes by the end of the week which will produce a strong south to southwesterly mid and upper level steering current for both of these tropical disturbances.  While the potential intensity of these disturbances are unknown, the potential for some degree of influence from these tropical features by the end of next week or into next weekend is growing.  Note, that if the cold front that approaches mid week stalls, the addition of a tropical system will make for some rather wet conditions for much of the East coast.

As for the next four days, weak high pressure will move over the forecast area with clear to scattered cloud cover, a threat for an isolated shower, light and variable winds, and temperatures averaging slightly above normal.  No significant organized low pressure system will influence the forecast area through this period and precipitation will be very light through this period as well in terms of the isolated showers.  The disturbances that do move through the forecast area will have highly localized influence on lifting and will likely have to rely on solar influences to destabilize the atmosphere enough to produce any shower or thunderstorm in the first place.

On Wednesday, the upper level trough will finally move towards the Great Lakes with a trough axis centered over the western Great Lakes.  This trough will be significantly tilted to a positive orientation which will lead to a strong southwesterly mid and upper level jet stream to develop from the Ohio Valley into New England.  Not only will this jet stream orientation inject a high level of tropical moisture from the Gulf of Mexico into the forecast area, but this orientation will cause the surface cold front to slow down and eventually stall over or just west of the forecast area by Wednesday afternoon.  We’ve seen this movie before!  The cold front will produce enough lifting to cause showers and thunderstorms to develop which will tap into the high level of moisture to allow the thunderstorms to intensify.  The potential for low level wind shear (surface winds from the south/southeast with upper level winds from the southwest/west) is also high, which may lead to more dynamic thunderstorms.

Another cold front will attempt to approach the forecast area on Thursday with similar results as the trough axis and upper level wind orientation will change very little.  As a result, another round of strong to severe thunderstorms will be possible along with the threat of flash flooding.

A third cold front will attempt to move through the forecast area as well, but with similar results.  One interesting twist in this story though is the interaction of what ever develops out of the two tropical disturbances in the Atlantic.  By this point, one of the tropical disturbances will be approach the Bahamas where upper level steering currents would force this tropical disturbance to turn to the northwest and possibly towards the East coast.

Temperatures through the period will average slightly above normal with highs ranging from the mid 80′s to lower 90′s and lows in the lower 60′s to lower 70′s.