Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 151 PM EDT Fri May 18 2018 Valid May 18/1200 UTC thru May 22/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS/UKMET evaluation...with preliminary preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Broad upper trough and embedded MCVs over the Southeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The model show similarly with this system. ...Upper trough crossing the upper Midwest this weekend... ...Cold front/surface wave crossing the region... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 75% 12Z GFS...25% 00Z ECMWF blend Confidence: Above average Minor differences remain with the 00Z ECMWF/CMC flatter with the base of the departing trough, resulting in a weaker surface low over southern Ontario. The model have been fairly consistent from run to run except the UKMET which has been oscillating between stronger and weaker. A blend with more weight toward the 12Z GFS/NAM/UKMET is preferred given better agreement in the ensemble spaghetti heights for weighting away from the weaker 00Z ECMWF/CMC. ...Large upper trough/closed lows over the West... ...Ejecting east across the central Plains this weekend... ...Crossing the Midwest by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z UKMET/12Z GFS Confidence: Below average Ensemble spread has decreased from yesterday, but there appears to be convective feedback in many of the NAM and global guidance which is causing problems with the QPF. Trends from the ensembles support more in the way of a 12Z GFS/12Z UKMET blend with the 00Z ECMWF farther north with the surface low across the Plains. The 12Z NAM is a seconary option early on but it tracks the surface low fastest to the east by late Sunday into Monday and the 00Z CMC is much slower/farther west with the surface low track which is not supported in the latest ensemble guidance. Confidence remains low due to the convective details influencing boundary locations. Please see the QPFPFD for details on precipitation. ...Upper trough digging into the West on Sunday... ...Energy lifting north out of the northern Rockies... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show good agreement with this system through Sunday night. Ensemble agreement is strong and trends have been small or toward the consensus so confidence is above average 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