A Climatology of Strong Cold Frontal Passages along the Colorado Front Range

Cold fronts significantly influence the climate and weather patterns observed across the Colorado Front Range, a region situated between the U.S. Great Plains and Rocky Mountains. In particular, these fronts contribute heavily to cool-season precipitation and can signal the onset of hazardous weather conditions such as extreme winds, temperature swings, and fire weather. This study adopts a statistical and physical approach to objectively classify strong cold frontal passages between 1950-2022 across eastern Colorado.

We utilized ERA5 reanalysis data to identify 724 strong cold frontal passages based on both the magnitude and spatial coverage of the temperature change following the cold frontal passage. A metric based on the magnitude of the equivalent potential temperature gradient and the temperature advection was also used to detect the location of fronts and the timing of their passage across the Colorado Front Range. Our analysis reveals that robust cold fronts peak in frequency during the shoulder seasons and tend to be more intense and concentrated in far Eastern Colorado away from topography. There is also a decline in the frequency of cold fronts during El Niño years as well as a relationship between frontal frequency and the phase of the Madden-Julian Oscillation. Composite analyses are subsequently performed over a North Pacific-North American domain to better understand the atmospheric conditions that precede these events as well as the variability of their impacts across the Colorado Front Range. Finally, we utilize time series plots centered on the time of frontal passage to examine the temporal evolution and variability of several key variables associated with strong cold frontal passages in the region.