The Front Range Blizzard of 1990. Part III: Numerical Simulations of Melting Effects

Abstract

Abstract The Front Range blizzard of 6 March 1990 resulted in heavy rain and snow along the foothills of Colorado and in southeast Wyoming. A narrow barrier jet with northerly winds behind a shallow mesoscale front developed concurrently with the heavy precipitation. It was hypothesized by Marwitz and Toth that the mesoscale front was the result of the diabatic process of melting. The CSU RAMS model was used to test the effects of melting, as well as the roles that the ice process and upslope flow played in the storm. A two-dimensional simulation was initialized with bulk microphysics and with a modified Flagler, Colorado, sounding. The results showed that the simulation was able to produce many features similar to the observations, such as surface cooling, a northerly barrier jet, and a steady. slow-moving shallow mesoscale front. It was found that these features were much less pronounced in an identical simulation but with melting turned off. Furthermore, it was found that diabatically cooled air was ac...