An Objective Cold Front Climatology for the Colorado Front Range

Cold fronts are crucial synoptic-scale meteorological features at midlatitudes. Locally in eastern Colorado, they are responsible for a large fraction of cold season precipitation and can serve as harbingers for high-impact weather events such as extreme winds, temperature “whiplash”, and dangerous fire weather conditions. The Colorado Front Range is located at the interface between the U.S. Great Plains and Rocky Mountains, which allows for complex interactions between synoptic-scale cold fronts and the local terrain. In the last few decades, attempts have been made to objectively analyze fronts using mathematical formulations and machine learning techniques. This study adopts a similar approach to objectively classify cold fronts between 1979-2022 specifically along the Colorado Front Range in order to construct a robust climatology for the region.

Utilizing a dataset of surface observations from cities across eastern Colorado and ERA5 atmospheric reanalysis data, we identify cold fronts based on the presence of strong, localized gradients in equivalent potential temperature. The objective scheme is subsequently applied to cases spanning multiple seasons, different times of the day, and fronts of varying strength in order to build a census of Colorado Front Range frontal passages. The resultant climatology will be used to analyze the seasonal and interannual variability in cold front frequency, intensity, and duration. Insights garnered from this study are expected to have implications for the forecast predictability of cold fronts and to inform local decision-makers of factors that influence the potential development of high-impact weather events.