Flash Flood in Allen County, Kentucky

Meader-Port Oliver Road was impassable due to flowing water over the roadway.

A negatively-tilted upper-level trough extended from the northern Great Plains down into the lower Ohio Valley on May 20th, bringing a strong cold front through the mid-Mississippi and Ohio Valleys. Showers and storms moved across the region along a warm front during the morning hours, limiting heating somewhat; however, a break in the precipitation during the early-to-mid afternoon hours allowed temperatures to warm into the upper 70s and low 80s with dewpoint temperatures in the upper 60s and low 70s. This lead to the development of around 2500 J/kg surface-based CAPE, which was combined with 50-55 knots of effective bulk shear to create an environment which was supportive of strong, organized convection.

The main wave of strong to severe storms with this event developed over the mid-Mississippi Valley during the mid-afternoon hours before moving into western and central Kentucky during the late afternoon and early evening hours. Storms evolved into a messy mixture of leading discrete cells and a trailing line which ultimately absorbed the lead cells as it moved quickly to the east-northeast. Downdraft CAPE values of 1100-1300 J/kg supported strong winds from collapsing thunderstorm cores making it to the surface, and a combination of downburst winds and strong winds from bowing segments within the line of storms resulted in scattered wind damage, mainly across south central Kentucky. Although storm motion was relatively fast, multiple areas of heavy rainfall moving over the same areas did result in isolated instances of flash flooding..