Characteristics and Climatology of Drylines Occurring Over the Higher Terrain of Southeast Wyoming

Commonly observed over the broadly-sloped terrain of the Southern Great Plains (SGP), drylines are frequent loci of warm season convection initiation. Drylines have been documented elsewhere, including over the Canadian prairies, Australia, and India. In this study, drylines occurring over the high terrain in southeast Wyoming (SE WY) just east of the Rocky Mountains were examined over a 3-year period (2010-2012) between the months of May-August. Observed on ~11% of the days within the analysis period, the surface moisture gradients associated with these drylines were quite strong, several times greater on average than the climatological mean moisture gradient typically found along the eastern slopes of the Rockies. Other characteristics of these drylines, including their relationship with the terrain and with localized convection initiation, were investigated. The synoptic conditions leading to their formation were also explored in an effort to aid local forecasters in anticipating their occurrence. Drylines which formed in SE WY were similar in some aspects to those found over the SGP, especially regarding their strength and propensity to lead to deep convection, but different in others. In particular, their frequency of occurrence, characteristics of diurnal motion, and the synoptic conditions driving their formation, differed noticeably.