Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 240 PM EDT Sat Jun 09 2018 Valid Jun 09/1200 UTC thru Jun 13/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Broad trough over the Northeast through Sunday... Preference: General model blend Confidence: Above average The models agree in having additional shortwave energy dropping southeast from Quebec and in across the Northeast through Sunday which will reinforce and actually sharpen the trough over the Northeast through Monday before it then begins to lift out. The latest models are in good agreement and so a general model blend will be preferred. ...Strong vorts over the Upper Midwest today... ...Crossing the OH Valley and Mid-Atlantic this weekend... ...Frontal zone from the Midwest to the Mid-Atlantic... Preference: Non-ECMWF blend Confidence: Average The guidance agrees in taking a couple of well-defined vort centers this morning (one over southwest MN, and one over northern IL) off to the east and southeast through the weekend which will bring collectively a mid level trough down across portions of the OH Valley and Mid-Atlantic region through Sunday and Monday. This will drive multiple waves of low pressure along a frontal zone that is draped from the Midwest to the Mid-Atlantic. The 12Z cycle of guidance has come into a bit better agreement with the placement of the front and the general vort/surface wave evolution, but there is one notable exception. The 12Z ECMWF now has a much stronger vort evolution involving the system over southern MN and it convectively amplifies its surface low much more so than any other model as it crosses the Midwest and approaches the OH Valley. The ECMWF with this wave becomes the slowest and farthest north solution. There is only modest spread with the timing and depth of the energy on the other models, and so a non-ECMWF blend will be preferred. ...Deep upper trough coming into the Northwest this weekend... ...Cold front sweeping out across the Plains by Monday... Preference: Non-NAM blend Confidence: Above average An anomalously strong upper trough is currently coming into the Pacific Northwest and will be bringing pronounced height falls and a strong cold front in across the Great Basin before then ejecting out across the Plains by Monday. There energy will then be crossing the upper Midwest by Tuesday. The models are in rather good agreement with the details of the height falls and timing features involving the front as well, but the 12Z NAM does appear a little too strong with its height falls across the northern Rockies and adjacent areas of southwest Canada. The 12Z CMC has trended toward the global model consensus with its slightly more progressive trend this cycle. Will prefer a non-NAM blend with this system. ...Upper trough approaching the Northwest on Tuesday... ...Offshore cold front/surface wave... Preference: Blend of the 12Z NAM, 12Z GFS and 12Z ECMWF Confidence: Above average The models show great agreement with the idea of another upper trough approaching the Northwest by Tuesday. A cold front should be positioned off the coast with a surface low west of Vancouver Island. The 12Z NAM, 12Z GFS and 12Z ECMWF are well clustered, with the 12Z UKMET and more so the 12Z CMC a bit slower. All of the models have similar agreement with their depth although the CMC appears perhaps a bit too weak. Will favor a blend of the NAM, GFS and ECMWF. ...Weak surface low along the SC coast... ...Upper trough over the Gulf of Mexico/Southeast... Preference: General model blend Confidence: Above average The agrees in taking the weak surface low near the SC coast this morning gradually off to the northeast near the eastern NC coastal plain through Sunday before then dissipating it. On the larger scale, the persistent upper trough over the Southeast and the Gulf of Mexico is expected to gradually weaken through the period, with just a modest weakness left over the Southeast by Tuesday. A general model blend will be preferred with these features. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison