Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 107 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 Initial 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 NAM/GFS Confidence: Average A slightly negatively tilted trough axis over the Pacific Northwest this morning swings northeast over the northern Rockies 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 GFS/NAM become more progressive with the leading trough/cold front over the northern Plains Wednesday night with the GFS slightly outpacing the NAM for trough progression through the Great Lakes Friday. Given the propensity for the GFS to be too fast, a compromise with the NAM is reasonable for now. Expect 12Z non-NAM guidance to become more progressive with their 12Z runs with this feature. Next trough moving into the Pacific Northwest Thursday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC General Model Blend Confidence: Slightly above average The guidance shows general agreement with the depth and progression of this feature into the Pacific Northwest late Thursday with the 00Z CMC notably more positively tilted and slower than the rest of the guidance making it an outlier. Low pressure moving northeast along Eastern Seaboard into this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/00Z 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 00Z UKMET is by far the deepest solution with a well defined cyclone developing off NC on Thursday before shifting north. the 12Z NAM and 00Z ECMWF/CMC have similar depth and timing and are 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: weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination.pdf Jackson