The SPC has been slowly creeping the Slight severe area northwards, as is no surprise. At this point, I think that the Slight will end up along the SE PA and through the northern parts of NJ going into Wednesday morning. SNE may also have a “See Text” threat past 14Z.
As we get closer to the zero hour, it’s become easier to decipher the model trends as far as where the warm front will be able to lift to and who is under the gun Tuesday night into Wednesday morning. The main area of concern will be NC/VA/SoMD where the dynamics and the warm sector can interact the most efficiently to produce severe weather in the form of a linear SSW-NNE line of storms along the cold front. The severe threat will extend up through the northern parts of the region, but as the SPC stated mid-level stability is more of a factor in areas north and west of the D.C. area, which means less reports and slightly weaker winds along with a lesser chance for tornadoes.
The GFS appears to have a better grasp on the timing, but the NAM’s instability parameters are much more favored due to the mesoscale nature of the event. However, as we saw with the severe event from two weeks ago, neither model had a true grasp on how unstable the LL air actually was. This could be attributable to the strong advection of low-level instability by the LL jet, which was likely mishandled and under-represented by the models.
All-in-all, I wouldn’t be surprised if this ended up being similar to our 11/16 event, with the severe reports shifted about 150-200 miles south. D.C. impact from the line of storms will likely be around 4-6 AM Wednesday morning.