Computer modeling varies a good deal regarding the upcoming southern storm system -- it presently has a good deal of moisture associated with it and a chunk of that will likely impact portions of the region between Tuesday and Wednesday. There's some uncertainty in how the rainy scenario unfolds as the storm system's mid level support detaches from the surface feature, with the mid level energy cutting off over the Midwest and Ohio Valley while the bulk of energy at the surface shoots ahead. This may very well be a saving grace in preventing a more widespread heavy rain event than what may ultimately unfold. The surface feature will be weakening as it approaches us so the trigger for a widespread rain will be less potent...however, there's still a lot of moisture poised to approach the region.
With the mid level/surface tandem pulling moisture up from the Gulf of Mexico we're going to have the prospect of some heavy rain at times within showers or storms. Just how and where those break out is going to be the devil in the details that we'll monitor over the coming days.
The GFS, for instance, is aggressive about suggesting heavy showers, perhaps some storms, on Tuesday night into Wednesday around portions of the region in one of its forecast runs. Other runs show a less robust scenario as far as heavy rain is concerned and show a more scattered approach to rainfall. However, the GFS and NAM both show quite a lot of moisture being pulled northward into the region, with precipitable rates of two or more inches for the region on Tuesday night into Wednesday morning. If the low were a bit more intense, a bit stronger, this would be a clear cut signal for a significant rain event across the region. However, it does not look to be an equal opportunity soaker.
The result of this may not be a steady or widespread soaking but there may very well be scattered areas of rain and thunder, some of which produce heavy rainfall as they move through the region between Tuesday and Wednesday. This could be a situation where some places get an inch or more of rain while others do not. The shower and thunder threat looks to continue into Wednesday morning before easing.