Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 242 AM EDT Thu Jun 21 2018 Valid Jun 21/0000 UTC thru Jun 24/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model evaluation...including preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper low crossing the mid MS/OH Valleys... ...Deamplifying over the Great Lakes by Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average The 00Z NAM tends to hang on to a somewhat stronger reflection of this system through the period as compared to the well clustered global models. A non-NAM blend will be preferred. ...Series of upper troughs crossing the Northwest through Friday... ...Energy ejecting out across the Plains/Midwest... ...Closed low development over the Intermountain West by Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z CMC/ECMWF/GEFS mean blend...first trough evolution 00Z GFS/ECMWF blend...second trough/closed low Confidence: Average The models are in rather good agreement with the first trough that crosses the Northwest and then advances downstream across the Plains and Midwest through Saturday and Sunday, although there is a fair degree of timing spread by the end of the period as the 00Z NAM/GFS solutions become more progressive than the 00Z CMC/ECMWF and especially 00Z UKMET. The non-NCEP models definitely maintain more energy back over the Midwest. The 00Z GEFS mean suggests that the NAM and GFS are too progressive with the lead trough, and tends to show a little more support for the CMC/ECMWF solutions. Will prefer a blend of the GEFS mean and the ECMWF/CMC with this trough. A second trough though will arrive across the Northwest by Saturday and amplify into a closed low which drops down across the Intermountain West by Sunday. By the end of the period, the 00Z CMC is likely a little slow with its closed low evolution, whereas the 00Z NAM looks like it may be a little too deep and especially with its height falls spilling out across the Plains. The 00Z UKMET also appears too deep with its closed low over western WY at the end of the period. The 00Z GFS and 00Z ECMWF are reasonably well clustered and tend to reflect the model consensus, so a GFS/ECMWF blend will be preferred with the second trough. ...Upper trough over the Northeast on Thursday... ...Next upper trough arriving by Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...initial trough on Thursday Non-NAM blend...second trough arriving by Sunday Confidence: Above average The models are in good agreement with the upper trough over the Northeast on Thursday which then begins to lift out. The next upper trough begins to arrive from Canada on Sunday. The 00Z NAM is a little faster than the model consensus and is a bit deeper than the global models with this second trough. A general model blend will be preferred with the initial trough followed by a non-NAM blend with the second trough. ...Weakening low center/MCV over the lower Rio Grande Valley... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The models are in very good agreement with the details of this weakening 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