Aug 4, 2018
A southerly flow pumped in plenty of moisture from the Atlantic while a slow moving cold moved into the area. Copious amounts of moisture ahead of the boundary led to showers and thunderstorms. Torrential downpours combined with convection training over the same areas led to some flooding and flash flooding. Some of the flooding lingered into the early morning hours of the 5th.
Source: NOAA National Weather Service Storm Events Database (event 775605). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Frederick County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.