For the past several days, a center of low pressure has remained stationary over Ontario, Canada. Its trailing cold front curved eastward through New England and the Mid Atlantic region and then westward across the Ohio River Valley and the lower watershed of the Missouri River.
Meanwhile, strong southerly winds swept copious Gulf of Mexico moisture into the Southern Plains, the lower Mississippi Valley and the Southeastern States. Along the stationary front, this hot, moist air clashed with cool, dry air north of the front, producing pockets of torrential rain that drifted eastward along the front. The tragic flooding in St. Louis and Eastern Kentucky represented the most extreme consequences of this atmospheric scenario.
As the central low creeps eastward across Eastern Canada, its trailing front will dip farther to the south, concentrating the heaviest rain along the Arkansas and Tennessee River Valleys. Of course, the excessively warm water of the Gulf of Mexico has fueled these flood events and will surely feed powerful hurricanes as the season progresses.
