Jul 30, 2016
A boundary remained overhead on the 30th of July. Hot and humid conditions led to an unstable atmosphere. The instability along with the boundary caused a few severe thunderstorms to develop. Thunderstorms merged across Montgomery, Howard and Baltimore counties and led very heavy rainfall that led to flash flooding. Catastrophic flash flooding occurred in Ellicott City, MD the night of July 30th.
Source: NOAA National Weather Service Storm Events Database (event 651430). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Montgomery County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.