Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 107 PM EDT Fri Aug 07 2020 Valid Aug 07/1200 UTC thru Aug 11/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z NAM/GFS Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overall weather pattern across the continental U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend, weighted toward the 12Z NAM/12Z GFS/00Z ECMWF Confidence: Average The overall pattern across the lower 48 will feature a broad upper ridge centered over the Southern Plains into northwestern Mexico. The main driver of synoptic scale fronts/lows will be with the jet stream focused near the U.S./Canadian border. An initial quasi-stationary front will remain draped from the Mid-Atlantic to the Lower Mississippi Valley. Aloft, a weakening upper level trough over the eastern 1/3 of the nation today will quickly track into the western Atlantic through Saturday. The models are fairly similar with this scenario. Across the north-central U.S., a cold front will move through the Dakotas by Saturday morning, stall over South Dakota and Minnesota late Saturday and lift north as a warm front into Sunday morning. This boundary will be influenced by shortwaves moving about a longwave trough/closed low moving across central Canada. The models show generally good agreement with this feature, with only minor timing/amplitude differences. The greater differences are noted to be with convectively driven mid-level vorticity maxima and mesoscale boundaries from heavy rainfall. There is no clear answer as to which model or cluster of models will verify best, but there have been trends in the guidance over the past 24-36 hours for more definition to these features near the 12Z NAM, 12Z GFS and 00Z ECMWF...with the 00Z UKMET/CMC less defined in the mid-levels. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml This product will terminate August 15, 2020: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Otto