The WRF Microphysics and a Snow Event in Chicago

This is an experiment to see how the Weather Research and Forecast model (WRF) Advanced Research WRF (ARW) can forecast localized heavy snow. We will examine a snow storm that occurred on December 8, 2005 in northeast Illinois. A large influx of very moist air moved into northeast Illinois during the afternoon of December 8, 2005. Air with the maximum moisture content was in the 900 to 850 hPa layer (1). This was an unusual concentration of moisture in this layer. Some of this moisture may have been from Lake Michigan. There were dynamic processes that provided enough lift to produce snow. The temperatures at that layer where in the range for spatial dendritic growth. We will test the model with several microphysics to see which one of the microphysics would produce the most precipitation in this case. The results of our simulations will be incorporated in our operational use of the WRF-ARW at WFO Chicago.

1. Labas, K., 2006, Probable Factors Contributing to the Meso-scale Snow Band Affecting Midway Airport and the December 8, 2005 Southwest Airlines Incident. Internal Web Document