Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 125 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 NAM/GFS Evaluation with Preliminary Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave crossing the Great Lakes/Ohio Valley through Sat... ...Associated cold front crossing the Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z UKMET 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 one exception is the 12Z UKMET has a stronger depiction of the 700-500 mb low which is unsupported in the remaining guidance. Otherwise, a blend (excluding the 12Z UKMET) looks best here. ...Tropical Storm Fay... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS, 12Z ECMWF 12Z UKMET 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, while the 12Z CMC slows down. The 00Z GFS, 12Z ECMWF and 12Z UKMET show decent agreement with one another and the 03Z NHC advisory for 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 12Z ECMWF/12Z ECMWF mean Confidence: 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 12Z UKMET is slowest while the 12Z CMC is also a bit slow. There is a moderate amount of spread in the latest ensemble spaghetti height plots, but the 12Z ECMWF mean appears to be a decent representation of the middle of the latest spread with the 12Z ECMWF nearest to its ensemble mean. ...Longwave trough axis moving into western Canada and the northwestern U.S. on Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS, 12Z ECMWF, 12Z UKMET 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 and 12Z CMC differ with the core of the closed low that tracks through Alberta and Saskatchewan when compared to the remaining deterministic and ensemble mean guidance. 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