Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 258 PM EDT Tue Jul 07 2020 Valid Jul 07/1200 UTC thru Jul 11/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Final Model Evaluation with Model Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Closed low moving east across south-central Canada through Friday Associated cold front crossing the northern Plains Wednesday/Thursday and the Great Lakes Friday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF/NAM/CMC with some 12Z GFS Confidence: Average A slightly negatively tilted trough axis over the Pacific Northwest swings northeast over the northern Rockies rest of today, closing over Alberta tonight. This low then shifts east across the Canadian Prairies through Thursday before opening and lifting northeast over northern Ontario on Friday. The associated cold front shifts onto the Montana Plains this evening and crosses the Dakotas through Wednesday night before crossing the central Great Lakes through Friday. The 12Z ECMWF became more progressive and in terms of progression of the leading trough/cold front from the northern Plains to the Great Lakes is quite similar to the 12Z NAM and 12Z CMC. The 12Z GFS slightly outpaces both with trough progression through the Great Lakes Friday/Day 3, but is not too far ahead to be totally discounted, just limited in the blend. The 12Z UKMET is notably flatter than consensus which makes it an outlier. Next trough moving into the Pacific Northwest Thursday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Slightly above average The 12Z global suite is in good agreement with the depth and progression of this feature into the Pacific Northwest late Thursday. The 12Z CMC came much more in line with the rest of the guidance, with a less positively tilted and therefore more progressive trough. Low pressure moving northeast along Eastern Seaboard into this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/ECMWF/CMC Confidence: Average A fairly weak cyclone is expected to move drift east-northeast across the Carolinas through Wednesday before turning northeast up the Eastern Seaboard Thursday/Friday as a mid-level ridge builds to the north across the northern Appalachians and New England. The presence of this ridge continues to suggest a slower solution. The 12Z GFS remains the most progressive guidance with the turn north on Thursday. The 12Z UKMET is a little less deep with the cyclone than the 00Z, but is even slower now and a notable outlier. the 12Z NAM and 12Z ECMWF/CMC were steady with their 00Z runs and have similar depth and timing and remain preferred at this time. Shortwave trough moving across New England Wednesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Above average Good agreement with this Day 1 shortwave trough crossing northern New England Wednesday. 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 with the 21Z issuance: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Jackson