Heavy Rain in Webb County, Texas

McPherson station measured 4.60 inches.

A heavy rainfall event across South Texas developed as a strong upper-level trough extended southward from the Great Lakes into Texas, providing large-scale ascent and enhanced positive vorticity advection. At the surface, a cold front pushed into the region and eventually stalled, serving as the main focus for lift while interacting with outflow boundaries from earlier convection. Ahead of the front, deep Gulf moisture surged northward with PWATs climbing to near or above the 99th percentile for early fall, creating an environment highly favorable for efficient rainfall production. Instability was plentiful, with CAPE values exceeding 2500 J/kg, supporting thunderstorm development, while modest shear allowed for organized clusters. Initially, convection initiated along prefrontal boundaries and central Texas storms drifting south, producing locally strong winds, but as storms slowed overnight, the primary threat shifted to hydrology. Slow-moving and training cells, fueled by abundant instability and anomalous moisture, wrung out widespread 1'2 inches of rainfall with localized amounts of 3'4 inches. This combination of deep tropical moisture, frontal convergence, upper-level support, and storm interactions ultimately produced the widespread heavy rain and scattered flooding concerns across the region--primarily in Laredo/Webb County.