Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 311 AM EDT Sat Jul 11 2020 Valid Jul 11/0000 UTC thru Jul 14/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation with Final Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave crossing the Great Lakes/Ohio Valley through Sat... ...Associated cold front crossing the Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models show minor differences in the timing and strength of the low to mid-level wave advancing through the Northeast today/Saturday night. The new 00Z UKMET scaled back its previously stronger depiction of the 700-500 mb low which was unsupported in the remaining guidance. Therefore, a general model blend will work well for this system. ...Tropical Depression Fay... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z NAM blend is closest to 03Z NHC advisory Confidence: refer to NHC discussion The latest guidance is in good agreement concerning the track of Fay until late Saturday when the 00Z NAM deviates west of the NHC track. The difference is relatively minor when compared to the remaining 00Z deterministic guidance, but enough to exclude it from the preference at this time concerning the track of Fay. ...Mid-level shortwave to cross the northern Plains to Upper MS Valley Sat, Ohio Valley Sunday, Great Lakes to the Appalachians Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Near the 00Z UKMET/00Z CMC/12Z ECMWF mean/00Z GEFS mean Confidence: Slightly below average The models begin to diverge with the timing of the trough as it reaches the OH Valley. The 00Z NAM and 00Z GFS are faster, especially the 00Z GFS when compared to the remaining deterministic guidance and the GEFS/ECMWF means. The 00Z UKMET/CMC sped up their timing relative to their 12Z cycles which is a good move. Poor run to run consistency exists with this feature as it reaches the Northeast by Tuesday morning in many of the models given a very complex interaction of vorticity maxima in Ontario/Quebec which leans the preference toward the middle ground of the ensemble means. The closest to the means is the 00Z UKMET and 00Z CMC at this time. ...Longwave trough axis moving into western Canada and the northwestern U.S. on Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z NAM blend Confidence: Average The models show a broad 500 mb trough and associated surface cold front moving across the Pacific Northwest and Northern Rockies Sunday to Sunday Night and Northern Plains Monday. Mainly minor timing differences were noted in the latest guidance, but the 00Z NAM differs with the core of the closed low that tracks through Alberta and Saskatchewan when compared to the remaining deterministic and ensemble mean guidance. This has some impacts with the NAM's timing over the Northern Plains as a cold front sweeps through the region Monday into Tuesday. 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