An Examination of Sudden Warming Events Associated with Cold Fronts in Iowa

Abrupt temperature increases have been documented accompanying the passage of some cold fronts. These warming events can raise the temperature by as much as 4oC in mere minutes, and can sometimes last hours. Previous studies in Oklahoma, focused primarily on nocturnal periods, have indicated that these events are caused by strong winds associated with frontal passage mixing warm, elevated air down to the surface. This study examined front-associated warming events, both nocturnal and diurnal, at five airports in Iowa from 2014 to 2016. Strong warming events were found to be rare and restricted mostly to nighttime hours. Altogether, 11.2% of cold fronts during this period produced at least one warming event. Fall months recorded the most events, and had the highest frequency of warming when normalized for total frontal passages. A coarse spatial analysis also found that warming events were more common in north-central Iowa. Comparisons between warming events and control periods revealed that warming generally occurred in the presence of weaker initial winds and stronger low-level thermal inversions. These results align with previous studies indicating that shallow inversions play a role in development of these events. They also show that while daytime warming events are rare, they do exist. Spatial results also suggest possible topographic influences, given the prevalence of warming events over Iowa’s flatter, more open areas