Flash Flood in Mesa County, Colorado

Thunderstorms developed over the Redlands area of Grand Junction late in the afternoon of September 4th, and remained there for 2-3 hours. Impacts began to be noticed around 6:45 PM MDT, with an LSR in the area of 1 ESE Redlands indicating Water out of the banks of nearby wash and running over Redlands Parkway in several areas. Approximately half an hour later, another LSR indicated that water running over the roadway in many areas along South Camp Road in the Redlands (Redlands 1SSE). Debris was also reported as having to be removed from Monument Road (Redlands 3SSE). In addition to the LSR'd events, properties were flooded, normally dry washes were overfilled, and water and debris inundated several roadways in the area. Additionally, social media reports indicated flooding along No Thoroughfare Canyon, Monument Road, and in the Devil's Kitchen area of Colorado National Monument. Once the rain stopped and the storms dissipated, a local spotter provided the total precipitation from this storm, which was a 2.33 inches.

On September 4th, precipitable water values increased to above normal values, with the 18z Grand Junction sounding showing 0.69 inches of precipitable water. To the west of eastern Utah and western Colorado, an area of weak rotation associated with a passing shortwave helped to provide extra lift. Morning sunshine helped to realized enough instability that, with all other factors present, thunderstorms developed over the higher terrain through the afternoon. These storms were capable of producing heavy rain, were not especially fast moving, and had a tendency to train over the same area for several hours.