Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 237 PM EDT Thu Jun 07 2018 Valid Jun 07/1200 UTC thru Jun 11/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper trough crossing the Northeast on Friday... ...Broader trough digging in by Saturday/Sunday... Preference: Non-UKMET blend Confidence: Above average The models agree in having one shortwave cross the Northeast on Friday which tends to amplify lift northeast across the Canadian maritimes on Saturday as a closed low evolves. However, there will be additional shortwave energy dropping southeast from Quebec on Sunday which will sharpen over especially northern New England. The 12Z UKMET is a perhaps a little slow in bringing the secondary surge of energy, and with the remaining guidance rather well clustered, a non-UKMET blend will be preferred. ...Vorts crossing the Central Plains/Midwest today... ...Crossing the OH Valley and Mid-Atlantic Friday/Saturday... ...Frontal zone from the Midwest to the Mid-Atlantic... Preference: 12Z NAM/12Z GFS blend...through 48 hours 12Z GFS/12Z GEFS mean blend...after 48 hours Confidence: Below average The guidance again takes shortwave energy and a couple of convectively induced vorts across the central Plains today and then off to the southeast over the next couple of days across the OH valley and the Mid-Atlantic region. The 12Z NAM and 12Z GFS are both a bit more developed with the initial energy ejecting across the central Plains, but then there tends to be somewhat better agreement downstream. Differences though become rather stark by Saturday and Sunday as additional energy upstream drops southeast across the Great Lakes, OH Valley and toward the Mid-Atlantic region. The 12Z ECMWF, 12Z UKMET and to some extent the 12Z CMC are farther north with their vort tracks and also have a frontal zone focused farther north. The 12Z NAM and 12Z GFS are farther south. This results in some significant latitudinal differences with the QPF placement given differences in MCS trajectories. The 12Z NAM by Sunday becomes problematic in a different way with a strong feedback vort/trough crossing the Midwest that results in a well-defined surface low. Given the strength of the troughing over southeast Canada this weekend and the surface ridging south of James Bay, the preference will be for a more suppressed frontal structure and evolution of shortwave energy. A blend of the NAM and GFS will be preferred through 48 hours, and then a blend of the 12Z GFS and 12Z GEFS mean after 48 hours. ...Deep upper trough coming into the Northwest this weekend... ...Vort energy over the High Plains by Sunday... Preference: Non-CMC blend...over the Northwest 12Z UKMET/12Z ECMWF/12Z GEFS mean...High Plains Confidence: Average The latest guidance strongly agrees in bringing a rather anomalous trough in across the Northwest U.S. this weekend with pronounced height falls and a strong cold front. There is rather good agreement with the details of the height falls and timing features involving the front as well, but the 12Z CMC does appear a little too slow with its trough evolution by the end of the period. Will prefer a non-CMC blend over the Northwest. Over the High Plains, it should be noted that some vort energy will be attempting to eject out of the base of the upper trough by Sunday, and the GFS in particular has a feedback vort that will be dismissed across the northern Plains. The 12Z NAM also has energy that becomes much too developed downstream toward the Midwest. The 12Z GEFS mean seems reasonable as a mass field alternative and has reasonable support from the 12Z UKMET and 12Z ECMWF solutions over the High Plains by Sunday. So, given the convective vort/feedback concerns of the NAM and GFS, will prefer a blend of the UKMET, ECMWF and GEFS mean as a result for this region. ...Upper low/trough over the Southeast... Preference: General model blend Confidence: Above average The models maintain a large scale weakness over the Southeast through the weekend. A broad upper trough and embedded closed low is agreed upon with the models in persisting, and thus a general model blend will be preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison