Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 100 AM EDT Sun May 20 2018 Valid May 20/0000 UTC thru May 23/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model evaluation...with preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave trough exiting the East through early Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. ...Cold front/surface wave crossing the Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. ...Upper trough/closed low over the central Plains today and crossing the Midwest by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS and 12Z ECMWF Confidence: Average The guidance is finally fairly well clustered with the evolution of this system, but there are still differences of note. The 00Z NAM gradually becomes a little slower and deeper than the global models as the energy crosses the Midwest. Regarding the global models, the 12Z CMC becomes the weakest solution. The 00Z GFS and 12Z ECMWF agree on depth, with just a little bit of a timing difference as the ECMWF remains a little more progressive. The preference will be to again lean toward a GFS/ECMWF blend. ...Upper trough digging into the West on Sunday... ...Closed low digging into the Southwest Monday and Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models continue to show very good agreement with the mass field evolution of this system with only some very modest depth spread noted toward the end of the period. Will prefer a general model blend. ...Mid level trough over the eastern Gulf of Mexico... ...Lifting up across the Southeast on Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-12Z CMC blend Confidence: Slightly above average The models gradually take a rather broad mid level trough and associated closed low up across the eastern Gulf of Mexico and into the Southeast U.S. over the next couple of days. The guidance has come into generally good agreement on just a weak surface reflection with an inverted trough. Regarding the energy aloft, the 12Z CMC is a bit of a faster outlier in bringing the energy inland. Will prefer a non-CMC blend at this point. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison