Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 245 AM EDT Mon Aug 10 2020 Valid Aug 10/0000 UTC thru Aug 13/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Weak troughing over the southeastern U.S. Tuesday and Wednesday. Preference: 00Z GFS, 21z SREF Mean, 12Z UKMET blend Confidence: Average Model forecasts take an existing MCV over the Lower Ohio Valley from Sunday morning, southeastward toward the Carolinas by Wednesday morning into the base of a developing trough. The models differ in strength regarding this feature with most showing a trough east of the Appalachians across the Southeast and a few models hint of embedded 850 or 700 mb circulation developing within the broad trough axis. The models show a well defined closed high over the Atlantic that will act as a blockade to prevent this trough from moving off the southeast coast. The GFS/NAM/UKMET show better than average overlap on the axis of the 700 mb trough, supported by the 21z SREF Mean. A blend of these solutions would mitigate minor differences in timing/phasing. ....Missouri and Arkansas... Preference: 00Z GFS, 12z ECMWF Blend Confidence: Slightly Below Average The models show a 700 mb ridge with possible embedded high moving east from the lower mS Valley into the southeast. A low level front and 700 mb trough/possible embedded circulation moves east from Kansas today into MO and AR Tue. The models differe ont he strngth and timing, with the 00z NAM strongest with a more persistent 700 mb low. The 21z SREF weakened the wave quickest. An intermediate solution like the 00z GFS/12z ECMWF is preferred until better agreement develops. ...Longwave troughing over the Northwest Tuesday-Wednesday... Preference: Blend of 12z ECMWF, 00z UKMET, 00z NAM Confidence: Average As a broad mid-upper level trough axis develops over the northwestern U.S. Tuesday into Wednesday, weak waves will emanate and progress onto thwe high Plains Tue night and move across the northern Plains on Wed. Further south, a lee trough develops in CO to near the KS border. The 00z GFS stands out with the amplification of a 700 mb wave ejecting northeast from SD across MN on Wed. and near the WI/MN border by Lake Superior 00z Thu. Caution is advised with the GFS in the upper MS Valley. 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 Petersen