Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 257 PM EDT Thu Aug 16 2018 Valid Aug 16/1200 UTC thru Aug 20/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper trough crossing the Midwest and Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS and 12Z ECMWF Confidence: Slightly above average While there is generally good agreement with the height falls ejecting out of the Midwest through Friday, the 12Z NAM, 12Z UKMET and to some extent the 12Z CMC all generally get out of phase with the 12Z GFS, 12Z ECMWF as the energy arrives across the Northeast this weekend. Will prefer a blend toward the GFS and ECMWF given better ensemble support for this cluster. ...Upper trough crossing the Midwest and Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models take the next in a series of troughs and dig it down across the central Plains this weekend. The 12Z NAM, 12Z CMC and 12Z ECMWF are the deeper solutions, with the 12Z UKMET and more so the 12Z GFS the weakest. The GFS actually appears also to be perhaps a bit too slow with its surface front over the Plains. At this point, a general model blend will be preferred to compromise between stronger and weaker camps. ...Trough digging across the Northwest by Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average A new upper trough and associated closed low will dig into the Northwest by Sunday. The 12Z NAM is a little more progressive than the global models with this feature, although all of the guidance generally has good agreement on depth. Will prefer a non-NAM blend here 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 Orrison