Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 303 PM EDT Sun Jul 12 2020 Valid Jul 12/1200 UTC thru Jul 16/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation with Final Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave troughing over the northeastern quarter of the U.S. Monday to Wednesday... Preference: Blend of 12Z NAM and 12Z ECMWF Confidence: Average A mid-upper level trough crosses NY/New England tonight and Monday, eventually moving off the New England coast on Tuesday. Weak waves of low pressure are expected to develop along the front from the northern Mid Atlantic to eastern New England. Slight timing differences persist as the mid-level closed low moves from eastern New England into the coastal waters. The 12z ECMWF moved the 700 mb low faster, so the 12z ECMWF/12Z CMC/12z NAM are in the middle, with the 12z GFS faster to move the low offshore. The 12z UKMET also moved the 700 mb low off faster, so the trend in the new 12z ECMWF looks good. ...Longwave trough axis moving through the north-central U.S. through Wednesday .. Preference: Blend of 12z CMC/12z ECMWF Confidence: Slightly Above Average The models show good overall agreement with a broad 500 mb trough and associated surface cold front moving across the Northern Rockies and Northern Plains tonight and Monday, then out of the northern plains to the upper MS Valley Tuesday. Some minor timing and amplitude differences were seen, with the 12Z GFS a bit faster and 12Z NAM slightly more amplified Tue. The 00Z-12z Canadian global and ECMWF represent the middle ground, but the differences among the are small enough to support a general model blend for the preference. The 12z GFS appears to lower 700 mb heights/sea level pressure near where it produces convection in southern WI/northern IL. The GFS might be suffering from a bit of convective/grid scale feedback, so the low pressure further south depicted in the 12z Canadian global/09z SREF Mean/12z ECMWF/12z NAM/00z ECMWF Ensemble Mean is preferred. 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