Pennsylvania is a region in which interactions between the complex land surface and the lowest few kilometers of the atmosphere exert substantial controls on the weather. For example, the motion of fronts and air masses is known to be affected by even just shallow barriers like the mountain ridges ubiquitous to Pennsylvania. These same topographical features also commonly alter precipitating weather systems, leading to tremendous rainfall and snowfall variability. The complex terrain of Pennsylvania can produce atmospheric circulations capable of triggering thunderstorms, in addition to influencing already mature thunderstorms and their attendant severe weather. Surface temperature and roughness differences between Lake Erie and the land surface of Pennsylvania routinely affect small-scale weather as well, with "lake-effect" snow bands being perhaps the most widely known of these lake-induced phenomena. It is even likely that the rapid population growth and associated development now occurring in central Pennsylvania will have an increasingly important effect on circulations near the ground.

The importance of interactions between the land surface and lower atmosphere, in not just Pennsylvania but in the entire Mid-Atlantic region, has been acknowledged by a virtually countless number of investigators over the years. However, these interactions and their associated phenomena have been largely unstudied owing to an absence of detailed observations. In a first attempt to alleviate some of these deficiencies in our understanding, the Penn State Department of Meteorology and the Center for Severe Weather Research teamed up to conduct the Pennsylvania Mobile Radar Experiment (PAMREX) during the fall months of 2003 and 2004. PAMREX used the Doppler On Wheels (DOW) radars to study a wide variety of phenomena, such as the interaction of fronts and thunderstorms with ridges and valleys, terrain-induced atmospheric circulations, and phenomena owing to atmospheric interactions with Lake Erie.