Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 242 AM EDT Sun Sep 23 2018 Valid Sep 23/0000 UTC thru Sep 26/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Final Model Evaluation...with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall preference for the entire CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/ECMWF blend Confidence: Slightly above average The models and ensemble means are indicating a transition from a quasi-zonal flow pattern across the northern tier of the nation to more amplified by Tuesday night as the Pacific Northwest trough at the beginning of the forecast period grows stronger as it tracks eastward. This in turn will fortify the upper ridge situated over the western Atlantic and a closed upper high over the northeast Pacific. Shortwave perturbations around the base of the large-scale central U.S. trough will be the main weather makers through the first half of the work week. The models show only modest timing and amplitude differences with respect to the wave of low pressure that should lift up across the Upper Midwest Sunday night and into Monday, with the NAM and UKMET among the faster solutions. The NAM and CMC are a little faster to bring the front southeast across the middle MS Valley and southern Plains compared to the other models, whilst the UKMET is slower and the farther north with the secondary low over the southern Plains Tuesday morning. With the disturbance approaching the southeast coast by midweek, the UKMET is a stronger solution compared to the model consensus, and similar to its previous runs. With respect to the lingering mid level low currently over the southern Plains and lower MS Valley, this system should gradually weaken and begin to dampen out over the next couple of days. A GFS/ECMWF blend is preferred to deal with placement differences Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml D. Hamrick