Mechanisms of Great Basin frontogenesis

Intense cold fronts traverse the Intermountain West several times per year and are often accompanied by high winds (> 30 m s^-1), power outages, dust storms, dramatic temperature falls, wild fire runs, and/or heavy snow. Previous studies suggest that diabatic processes, such as differential sensible heating and evaporative cooling, as well as orographic effects, like enhancement of the confluent deformation field downstream of the Sierra Nevada, play a role in this arid and topographically complex region. The Great Basin has been established as an area of frequent frontal intensification, yet the relative importance of these mechanisms in the frontogenetical process over the region have not yet been elucidated. This study examines a case known as The Tax Day Storm, which features one of the most powerful cold frontal passages in Salt Lake City history. Our results show that diabatic effects play a dominant role in decreasing postfrontal temperatures, while prefrontal temperatures remained relatively unchanged. Further, WRF model simulations with and without the Sierra Nevada establish the role of the these mountains in creating a prefrontal area of confluent deformation. This axis of dilatation downstream of the Sierra also affects the movement of the front, ultimately retarding its eastward progress. These results quantify the role of these mechanisms in Great Basin frontogenesis for this case, furthering our understanding of the complex evolution of these storms.