Use of a mesoscale model to forecast severe weather associated with a cold front aloft

A forecast of severe weather and the potential for tornadoes associated with a cyclone that developed in the lee of the Rocky Mountains on 19-21 June 2000 is evaluated. The forecasting methods used by the National Weather Service for this case, which focused on the position of a surface trough and the location of favorable quasigeostrophic jet dynamics, poorly predicted the extent and location of the severe weather. Application of a conceptual model for cyclones east of the Rockies, which highlights the importance of cold fronts aloft (CFA), shows that a CFA was an important trigger to convection in the 19-21 June 2000 cyclone. A simple forecasting method is demonstrated that emphasizes the importance of lifting for cases that involve CFA. This method is applied to the 19-21 June 2000 cyclone and is found to improve greatly the determination of where severe weather occurred.