Dense fog climatology for the Blue Ridge foothills and piedmont areas of the Blacksburg, VA county warning area for the period 1973-2008

WFO Blacksburg issues Terminal Aerodrome Forecasts (TAFs) for five airports. Dense fog with visibilities of a half mile or less producing VLIFR conditions is a frequent forecast problem at individual airports. In addition, dense fog occasionally becomes widespread enough to necessitate a Dense Fog Advisory. Historical dense fog data is available for each of the five airports. The locations of three of the airports, Roanoke, Lynchburg, and Danville, represent a climatological region with similar geographical characteristics on the east side of the Appalachian Mountains. Thirty six years of fog data (1973 through 2008) from these airports were studied to produce a climatology of dense fog events. Although a quarter of a mile or less visibility is the threshold for a dense fog advisory, we found that we needed to use visibilities of a half mile or less in order to get a large enough sample for the study. A dense fog event was then defined as one in which 2 of the 3 airports recorded dense fog of a half mile or less for at least 2 hours during the same period. A period of two hours or longer would have a major impact on aviation and ground travel, and with the similar topography and relative close proximity of the three airports, the dense fog was then probably extensive enough to warrant a dense fog advisory. 176 separate events were identified in the 36 year period. Jan Jackson, Ken Kostura and William Perry. "February 2011." System requirements: Adobe Acrobat Reader. Includes bibliographical references (pages 11-12). 2011 NWS (National Weather Service) ER (Eastern Region) Library Public Domain 1931