Synoptic and mesoscale aspects of an Appalachian ice storm associated with cold-air damming.

Though surface temperatures were initially below freezing in most of this region, objective guidance indicated that large-scale warm advection would render the atmosphere conductive to rain. Warm advection did occur above about 900mb, but below this level warm advection was prevented by a cold wedge-shaped ridge of high pressure which became entrenched along the E slopes. Temperatures in the lowest 0.5-1km remained below freezing and and an ice storm resulted. This case study documents the evolution of the wedge ridge and the temperature and wind fields associated with it. Comparisons are made between the evolution of these fields within the quasi-stationary wedge ridge (a weather regime known as cold-air damming) and their evolution during the preceding period, when the pressure ridge was progressing E across the Midwest. Apparently due to the lack of vertical resolution sufficient tp capture such features, operational numerical models exhibited substantial errors in this case.-from Authors