Relationships between NW flow snowfall and topography in the Southern Appalachians, USA

Abstract

NW flow snowfall (NWFS) events are common occurrences at higher elevations (1500 to >2000 m a.s.l.) and on windward slopes in the Southern Appalachian Mountain region of the south- eastern USA. The spatial patterns of NWFS are strongly controlled by topography, resulting in pro- nounced spatial variability. The strong topographic and low-level convective forcing, coupled with low temperatures and strong winds, increases societal impacts. This paper analyzes the relationships between NWFS and various topographic and geographic (TOPO/GEOG) variables in the Southern Appalachians. We identified NWFS events on the basis of low-level wind direction, extracted values for the TOPO/GEOG variables from Digital Elevation Models (DEMs), and developed statistical rela- tionships between NWFS and the TOPO/GEOG variables. Using a multivariate regression model and GIS techniques, we also mapped mean annual NWFS across the region. Results indicate that eleva- tion and NW exposure are most strongly correlated with NWFS; however, the strength of these rela- tionships is mediated by temperature. In the colder NWFS events, the relative importance of eleva- tion is diminished, while NW exposure and distance to a NW slope are relatively more important. Additionally, we demonstrate that multivariate regression modeling in conjunction with GIS tech- niques can be an effective way to map snowfall patterns associated with specific wind directions, particularly when a strong topographic control is evident.