Debris Flow in Hinsdale County, Colorado

Colorado Department of Transportation reported the closure of Colorado State Highway 149 at mile marker 74, roughly 1 mile north-northwest of Lake City, due to a mudslide. This area is very steep, and prone to rock and mudslides with either prolonged moderate to heavy rainfall, or short but intense heavy rainfall.

Conditions for organized convection were less favorable on August 19th in comparison to previous days, with plenty of moisture but very limited upper level support or instability. However, the terrain of western Colorado acts as a source of lift, and differential daytime heating between the lower and higher valleys can add a boost of instability to that already present with the abundant monsoonal moisture. It was just this scenario on the afternoon of the 19th that allowed showers and storms to form over the San Juan mountains over Hinsdale county. The abundant moisture combined with slow storm motion to increase the threat of heavy rain, flash flooding, and debris flows across that area.