Observational Analysis of Cold Air Damming (CAD) in the Mid-Atlantic Region
Eric Allen, University of Delaware, Newark, DE (allenea@udel.edu)
Andrew Synder, NOAA/NWS Weather Forecast Office, Sterling, VA
Michael Muccilli, NOAA/NWS Weather Forecast Office, Sterling, VA
Matthew Elliott, NOAA/NWS Weather Forecast Office, Sterling, VA
Howard Silverman, NOAA/NWS Weather Forecast Office, Sterling, VA

Abstract:
Warm frontal passage throughout the Mid-Atlantic region is often complicated by terrain effects attributed to the Appalachian Mountains (e.g., cold air damming-CAD).  Situations of CAD-like behavior often occur with retreating Arctic air masses ahead of and/or with the onset of southerly or southwesterly flow in the boundary layer (below 850 hPa).  Near surface dense cold air often takes longer to mix out in areas in which southerly flow is blocked by relatively higher terrain to the north/west.  This slow mixing-out process of the “cold pool” is often not handled well by even the current suite of operational high-resolution (less than 4km grid resolution) mesoscale weather prediction models. This, in turn, leads to forecast challenges of high impact weather, such as occurrence of freezing rain and (for aviation operations) persistence of very low cloud ceilings.  Surface and upper air observations and geographical features were analyzed to determine environments conducive to keeping cold air trapped near the surface. We also examined which observations helped shed light on mechanisms that aid in forecasting CAD erosion.