Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Sun Jul 12 2020 Valid Jul 12/0000 UTC thru Jul 15/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation with Final Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave troughing over the northeastern quarter of the U.S. Monday to Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 00Z NAM, 00Z GFS and 00Z UKMET Confidence: Average After the departure of a compact vorticity max from the Northeast early today/Sunday, a pair of shortwaves will approach the region from the west, helping to reinforce upper level troughing over the region into the middle of the week. The latest guidance shows good agreement with the first shortwave expected to reach the Mid-Atlantic region by Monday morning, but differences begin to show up with a compact mid-level closed low approaching New York late Monday. The 00Z ECMWF is the slowest while 00Z CMC more progressive than the favored middle ground supported by the 00Z NAM/GFS/UKMET and the latest ensemble means. Ensemble spaghetti height plots show a fair degree of possibilities but the best clustering is in the middle of the faster and slower solutions. ...Longwave trough axis moving through western Canada and the northwestern/north-central U.S. through Wednesday morning.. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend weighted toward 00Z NAM/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 Pacific Northwest and Northern Rockies Sunday and Northern Plains Monday. Some minor timing differences were seen, with the 00Z GFS a bit faster and 00Z NAM a little slower. The 00Z NAM/ECMWF represent the best middle ground, but the differences among the remaining models are small enough to support a general model blend for the preference. 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