Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1249 PM EDT Tue Jul 14 2020 Valid Jul 14/1200 UTC thru Jul 18/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation with Preliminary Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave troughing over the northeastern quarter of the U.S. Monday to Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models show similarly with this system. Any differences, which correspond to a departing offshore surface low located east of Nova Scotia, appear once this system's impacts have left the Northeast. Therefore, a general model blend can still be used. ...Longwave trough axis moving through the north-central U.S. through Wednesday with accompanying surface cold front... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS...14/00Z ECMWF/UKMET blend Confidence: Average As a large closed low and associated longwave trough axis track eastward across southern Canada through the rest of the week, a corresponding cold front will move into the Great Lakes and Great Plains. With the 14/12Z GFS mass fields aloft maintaining a high degree of continuity, differences related to a shortwave tracking through the base of the trough on Wednesday remain--the GFS being on the faster side of the guidance. Still think that 14/12Z GFS, 14/00Z ECMWF/UKMET are in good enough agreement to each other to prefer a blend of them. ...Cut off low west of California by Thursday morning and progressive trough crossing the Pacific Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 14/00Z UKMET blend Confidence: Average The latest models continue to show good agreement with a 700-500 mb low closing off by mid-week over the western U.S. and retrograding offshore of California by late in the day Wednesday. There is also good agreement, albeit minor amplitude differences, with a progressive mid-level trough axis into the Northwest on Thursday. A general model blend represents both systems along the West Coast well. 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