Mount Holly afternoon AFD mentions the shortwave and storm chances this evening/overnight-
Latest analysis shows a very subtle boundary straddling the Delmarva and southern NJ on a southeast-northwest alignment. This boundary, after pushing south across the region overnight, will move back northeast across the region this evening into tonight. Dew points remain sultry on the south side of this boundary, but to the north, temperatures and dew points are running just a bit shy of expectations, keeping heat indices lower than expected. That said, will retain heat headlines as-is even though it looks like we may be falling short. Aloft, a notable shortwave is over the Appalachians to our west, heading east. This looks to be the trigger for thunderstorms now developing in that general vicinity. Expect these to continue moving generally eastward thru the rest of the afternoon into the evening, possibly crossing a majority of the region, but most likely areas from Philly south and west. They will be feeding on the weak shear with the aforementioned shortwave and the plentiful CAPE (over 2000 j/kg) just south of the aforementioned boundary. This will therefore provide at least a marginal risk of severe weather, so SPC has added these areas to the marginal risk. Will need to watch convection and instability trends closely this evening, as its not out of the question a further ramp-up is eventually needed, but for now am comfortable with current forecast. Shortwave moves on by overnight, but then remnants of developing MCS`s further west may come into play. Lots of uncertainty here, with some guidance showing them holding together late tonight into early Saturday, while others completely dissipate them as they cross the mountains. Thus, have slight chance POPS for most late tonight into Saturday morning.