The Madison County, Virginia, flash flood of 27 June 1995

Between 25 and 27 June 1995, excessive rainfall and associated flash floodi ng across portions of western Virginia resulted in three fatalities and mil lions of dollars in damage. Although many convective storms occurred over t his region during this period, two particular mesoscale convective systems that occurred on 27 June were primarily responsible for the severe event. T he first system (the Piedmont storm) developed over Madison County, Virgini a (eastern slopes of the Blue Ridge Mountains), and propagated slowly south ward producing 100-300 mm of rain over a narrow swath of the Virginia footh ills and Piedmont. The second system (the Madison storm) developed over the same area but remained quasi-stationary along the eastern slopes of the Bl ue Ridge for nearly 8 h producing more than 600 mm of rain. Analysis of this event indicates that the synoptic conditions responsible f or initiating and maintaining the Madison storm were very similar to the Bi g Thompson and Fort Collins floods along the Front Range of the Rocky Mount ains, as well as the Rapid City flood along the east slopes of the Black Hi lls of South Dakota. In all four events, an approaching shortwave aloft cou pled with high-level difluence/divergence signaled the presence of local as cent and convective destabilization. A postfrontal ribbon of relatively fas t-moving high-theta(c) air, oriented nearly perpendicular to the mountain r ange, provided a copious moisture supply and helped focus the convection ov er a relatively small area. Weak middle- and upper-tropospheric steering cu rrents favored slow-moving storms that further contributed to locally exces sive rainfall. A conceptual model for the Madison-Piedmont convective systems and their sy noptic environment is presented, and the similarities and differences betwe en the Madison County flood and the Big Thompson, Fort Collins, and Rapid C ity floods are highlighted.