Extratropical cyclones are major contributors to consequential weather in the mid-latitudes and tend to develop in regions of enhanced cyclogenesis and progress along climatological storm tracks. Numerous studies have noted the influence that terrestrial snow cover exerts on atmospheric baroclinicity which is critical to the formation and trajectories of such cyclones. Fewer studies have examined the explicit role which continental snow cover extent has in determining cyclones intensities, trajectories, and precipitation characteristics. While several examinations of climate model projections have generally shown a poleward shift in storm tracks by the late 21st century, none have determined the degree to which the coincident poleward shift in snow extent is responsible. A method of imposing 10th , 50th , and 90th percentile values of snow retreat between the late 20th and 21st centuries as projected by 14 Coupled Model Intercomparison Project Phase Five (CMIP5) models is used to alter 20 historical cold season cyclones which tracked over or adjacent to the North American Great Plains. Simulations by the Advanced Research version of the Weather Research and Forecast Model (WRF-ARW) are initialized at 0 to 4 days prior to cyclogenesis. Cyclone trajectories and their central sea level pressure did not change substantially, but followed consistent spatial trends. Near-surface wind speed generally increased, as did precipitation with preferred phase change from solid to liquid state. Cyclone-associated precipitation often shifted poleward as snow was removed. Variable responses were dependent on the month in which cyclones occurred, with stronger responses in the midwinter than the shoulder months.

A feature-based metric of the waviness of the wintertime, Northern Hemisphere polar and subtropical jets is developed and applied to three different reanalysis data sets. The analysis first identifies a “core isertel” along which the circulation per unit length is maximized in the separate polar (315:330K) and subtropical (340:355K) jet isentropic layers. Since the core isertel is, by design, an analytical proxy for the respective jet cores, the waviness of each jet is derived by calculating a hemispheric average of the meridional displacements of the core isertel from its equivalent latitude - the southern extent of a polar cap whose area is equal to the area enclosed by the core isertel. Analysis of the seasonal average waviness over the time series of the various data sets reveals that both jets have become systematically wavier while exhibiting no trends in their average speeds. The waviness of each jet evolves fairly independently of the other in most cold seasons and the slow northward creep of the polar jet is statistically significant. Finally, comparison of the composites of the waviest and least wavy seasons for each species reveals that such interannual variability is manifest in familiar large-scale circulation anomalies.