Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 237 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. ...Upper trough/cold front crossing the 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: Non-NAM blend Confidence: Average The guidance is finally fairly well clustered with the evolution of this system, but there are still differences of note. The NAM gradually becomes a little slower and deeper than the global models as the energy crosses the Midwest. Regarding the global models, there is notably better agreement as the ECMWF has slowed down a little more and also the CMC and UKMET have clustered toward the GFS solution. Based on the latest trends and clustering, a non-NAM blend will be the preference. ...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: General model 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. Model spread is rather minimal at this point as the CMC has trended slower and in line with the remaining guidance. Thus, will prefer a general model blend. ...Shortwave energy/vorts lifting across the Plains Tuesday and Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z UKMET and 00Z ECMWF Confidence: Average Multiple shortwave impulse are expected to lift northeast out of the base of the Western U.S. trough and across the Plains on Tuesday and Wednesday. The NAM and GFS are both rather aggressive with their respective vorts and appear too strong considering that the energy will be lifting northeast into a mean layer ridge. There is evidence of convective feedback over deepening this energy on both models. The CMC, UKMET and ECMWF all appear more reasonable with the strength of their vorts, although the CMC does look too deep with the energy it has over MN/IA at the end of the period. Will favor a UKMET/ECMWF blend in general with the energy attempting to eject out across the Plains Tuesday and Wednesday. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison