May 1, 2020
A period of heavy rainfall occurred downstream of a highly amplified trough April 30th into May 1st. A strong low-level jet transported a moisture rich airmass into the area, and strong synoptic scale ascent downstream of the closed upper low produced a soaking rainfall. Rainfall totals ranged from 1-2 inches across the area, producing river flooding in Maryland on May 1st and 2nd.
Source: NOAA National Weather Service Storm Events Database (event 894245). 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.