The West Virginia Historic and Devastating Floods of 23 June 2016: Summary of Impacts and National Weather Service Decision Support Services

During the daytime on 23 June 2016 several waves of organized deep convection moved over the central portions of the Appalachian Mountains from central West Virginia (WV) into west-central Virginia (VA), just south of a nearly stationary frontal boundary and in the vicinity of an outflow boundary.  A review of the synoptic pattern, important atmospheric anomalies, and convective-allowing numerical model signals can be found in a companion presentation by Grumm 2017. Primarily between 7 AM and 8 PM local time, rainfall totaled as high as 200-250 mm, with rain rates of over 100 mm/hr for much shorter periods. The rainfall in several WV counties on the western slopes of the Appalachians, including Greenbrier, Fayette, and Nicholas, suggested as much as a 1-in-1000 year event according to annual exceedance probabilities (AEP), and as much as a 1-in-500 year event across several other counties including Alleghany County in far western VA.

As a result of this extreme rainfall in a relatively short period of time, in conjunction with nearly saturated antecedent soil conditions and the steep terrain of the region, devastating flash flooding and record flooding on several gauged streams and small rivers occurred.  Thousands of homes and business were damaged or destroyed, road repair costs are expected to exceed 50 million dollars, and sadly there were 23 fatalities (the highest in the state of WV since November 1985 floods when 47 died). Fifteen of these deaths on 23 June occurred in Greenbrier County WV.  During the flooding, numerous water rescues and evacuations were conducted, and more than 2000 people were temporarily displaced.  A State of Emergency was declared by the Governor of WV for 12 counties.

While the extreme degree of flooding was not anticipated well in advance, the potential threat for flash flooding was recognized and communicated well in advance through briefings and the issuance of a Flash Flood Watch on the afternoon of 22 June. Radar-based rainfall estimates, and especially the Multi-Radar Multi-Sensor (MRMS) products recently made available to National Weather Service (NWS) forecasters in real time, proved very accurate when compared to rain gauge readings in the area.  This is especially worth documenting given portions of this area suffer from partial beam blockage and are at relatively far distances from area radars. During this event, the NWS offices in Charleston WV and Blacksburg VA combined to issue 21 Flash Flood Warnings with lead times averaging over two hours; three of these warnings included the relatively rare “flash flood emergency” wording based on coordination between the NWS and local emergency officials. Rare and serious wording was also used in several of these warnings and statements. Phone calls and emails from the NWS to local officials during the event also resulted in potentially life-saving actions, including decisions to deploy swift water rescue teams and the evacuations of over 200 people in one county. Social media and “NWSchat” software was used to communicate the extreme threats as well. Briefings were also provided for a number of days following the event to assist with recovery efforts, and phone calls were made to officials as needed for any threatening weather. Lessons learned from this event will be presented along with best practices for communication of future extreme flash flood events.