Evaluation of WRF forecasts of fog events against observations during MATERHORN Fog-X

Cold air pool events develop in mountain basins during winter months due to topographic trapping of cool, dense air. This air can become significantly decoupled from the warmer, more turbulent air above the mountain barrier and can provide a preferential fog environment. During January 2015, the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Fog-X field campaign was held in the Salt Lake and Heber Valleys of northern Utah to investigate the processes of fog formation and evolution. The Weather Research and Forecasting (WRF) model was used to provide real-time forecasting during the campaign. Three fog events were observed: 8-9, 9-10, and 15-16 January. The primary objective of this study is to evaluate the accuracy of WRF forecasts in terms of the fog onset and dissipation. WRF model outputs are compared with observed visibility, sounding data, and surface observations collected during the field campaign. The performance of the WRF in fog forecasting, implications of the results for additional studies, as well as controlling factors that influence fog development will be discussed in the presentation.