Banded convection in Colorado snowstorms: insights obtained from X-band radar observations and numerical simulations

During several snowstorms along the Front Range of Colorado in the spring of 2013, convective bands were embedded within the broader envelope of precipitation. These bands were responsible for substantial small-scale variations in the accumulation of snowfall at the surface, and the intense snowfall rates in the bands resulted in transportation disruptions in the heavily populated urban corridor. Of particular interest are the convective snowbands that occurred on 23 March and 15 April 2013, which were sampled by the CSU-CHILL radar operating at X-band. In this presentation, these radar observations will be analyzed in conjunction with the output of convection-permitting numerical simulations to reveal the dynamical and microphysical processes at work in these events. Preliminary results reveal two findings for these snowbands along the Front Range: (1) extremely efficient growth of large aggregates within the convective updrafts, and (2) a west-east oriented standing wave that developed downstream (south) of the Cheyenne Ridge in northern Colorado, causing reduced snowfall in the downward branch and enhanced snowfall in the upward branch. These results and further details of this integrated observational and model-based analysis will be presented at the conference.