Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 119 PM EDT Mon Jul 02 2018 Valid Jul 02/1200 UTC thru Jul 06/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS evaluation including preliminary preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper trough advancing into Ontario/Quebec tonight with accompanying cold front into the Northeast and Ohio Valley... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. ...Westward moving upper circulation along the Gulf Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS / 00Z ECMWF blend Confidence: Average Biggest differences are regarding strength of this feature with the 00Z CMC strongest and considered least likely to verify given a lack of support. Some combination of the stronger/more suppressed tracks is preferred best represented by a 12Z GFS/00Z ECMWF blend. ...Upper low approaching the southeastern U.S. coast by mid-week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z GFS blend Confidence: Slightly above average Some minor timing differences as the mid-upper wave nears the Southeast coast but the 12Z GFS trended faster than most guidance by Wednesday night into Thursday, so will leave it out of the preference for that reason. ...Upper low/trough taking shape over Canadian Rockies/Pacific Northwest Mon/Tues...lifting across Northern Plains/S Canadian Prairies into Wed/Thurs. Surface wave(s) along Northern Plains frontal zone. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Preference: 12Z NAM/12Z GFS blend Confidence: Slightly below average Biggest uncertainty with systems across the lower 48 is here with above average ensemble spread and poor run to run consistency. Convective feedback in the vicinity of a frontal boundary across the north-central U.S. adds another layer of complexity to the forecast. The timing of the upper wave in the 00Z ECMWF appears a bit too fast given the latest ensemble clustering and the fact it is faster than its own ensemble mean. The 12Z GFS is slower/deeper, but not to the degree of the 00Z CMC, with the 00Z CMC likely a poor choice. Regarding the frontal boundary into the north-central U.S. and related surface waves, a blend of the 12Z NAM/GFS is preferred overall, but with low confidence. ...Shortwave reaching Canadian West Coast and becoming closed low off U.S. West Coast by late Wed/Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models show similarly with this system. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto