Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1158 AM EDT Thu Apr 18 2019 Valid Apr 18/1200 UTC thru Apr 22/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Longwave trough closing off over TN Valley Friday Then Moving Into Mid-Atlantic By Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12z GFS/06z GEFS and 00z ECMWF/ECENS Confidence: Average Longwave trough currently over the southern Plains today will move eastward and eventually close off over the Tennessee Valley Friday then move into the central Appalachians and Mid-Atlantic Saturday and Sunday. In general, model agreement is fairly good at the mid/upper levels with some minor differences noted at 500 mb. The 00z ECMWF is a bit slower by 12z Saturday compared to the faster NCEP suite (GFS/NAM) and by 12z Sunday, is also suppressed further to the south compared to the GFS/NAM which takes the trough axis more negative tilted. At the surface, model differences begin by 12z Friday where the ECMWF has the surface low over western KY while the GFS is over northern KY while the NAM/UKMET/CMC lie across central KY. The GFS continues to take on the NW side of the model spread Friday compared to the rest of the guidance though by Saturday, most of the guidance ends (except the UKMET) ends up fairly similar in the low position. The GFS and its ensemble mean are fairly clustered together while the ECMWF and its mean are also very similar. A blend of the two would probably yield a favorable result and is the preference at this time. ...Short wave crossing the Pacific Northwest and Northern Rockies Fri and Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 12z Saturday, then non-CMC blend Confidence: Slightly above average There is fairly good model agreement and run to run consistency with the shortwave trough pushing into the Pacific Northwest Friday and Saturday. Between the 00z and new 12z data coming in, there is very good agreement through Saturday 12z such that a general model blend is preferred. Beyond that time frame, more model differences creep up. The CMC is a flatter, open, and more progressive wave compared to the rest of the guidance by Sunday. Meanwhile, the rest of the guidance attempts to close off in the mid/upper levels and there is fairly good agreement with that idea through Sunday 12z. Given this agreement and the outlier solution in the CMC, will suggest a non-CMC blend for the forecast period. ...Long wave trough crossing the Baja Peninsula Fri/Sat into Southern/Central Plains Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average There is tight clustering between the operational guidance with the compact shortwave trough crossing through the Baja Peninsula Friday and Saturday that then moves through the southern Rockies and into the southern/central Plains Sunday. With the much above average model agreement and confidence, a general model blend is preferred. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Taylor