Latest AFD from Mount Holly-
A strong, slow moving coastal storm will affect the region for most of the weekend. Widespread rain will be ongoing early Friday night as a warm front sits south of our region. Primary low pressure over the Ohio Valley will weaken Friday night as a secondary low develops just off the Delmarva coast in response to an approaching upper level trough and strong low level frontogenetic forcing. That secondary low will continue to develop off the coast and sit with little movement Saturday into Sunday, before strong high pressure to the north begins slowly forcing it south. The low will also start to become vertically stacked during this time as the upper level trough closes off and moves over the surface low. This will cause the surface low to start slowly weakening, but thanks to strong high pressure to the north, the pressure gradient will remain very strong, reinforcing the onshore flow.
This is quite an anomalous system for the season, a true Nor`easter with multiple days of rain and battering wind likely especially at the coast. The steadiest rain is expected from Friday night through Saturday, but periods of rain and showers are likely to continue into Sunday. We`ll first deal with the initial thump of overrunning precipitation, which will be what starts during the daytime on Friday. As the coastal low spins up, we`ll then see areas of banded frontogenetic precipitation on its northwest flank which will continue to bring areas of rain through Sunday. With time on Sunday, as the low slowly shifts further south, northern portions of the area may dry out, while showers likely continue to the south and east.
Temperatures will also be a story this weekend. The combination of rain, a thick cloud deck, and strong onshore winds will lead to much below normal temperatures both Saturday and Sunday. Highs mostly in the low to mid 50s are expected, and a lot of time will be spent in the 40s. Combined with the wind and rain, the weekend looks downright ugly overall.