Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1224 PM EDT Sun May 06 2018 Valid May 06/1200 UTC thru May 10/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Trough deamplifying as it pushes through the Mid Atlantic today, with weak surface lows developing just offshore... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show sufficient model mass field agreement that a general model blend can be preferred with this energy. ...Upper level trough digging into the Great Lakes today and sweeping across the Northeast Monday... ...Associated cold front pushing through the Midwest and Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Models are also in very good agreement with this system, other than some minor differences in the mass fields. Will prefer a general model blend. ...Shortwave crossing the Northwest and arriving across the Northern Plains by Tuesday... ...Lee cyclogenesis over the Plains... ...Secondary shortwave dropping southeast over the Northern Plains along with an attendant front on Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS and 00Z ECMWF Confidence: Average The shortwave trough moving across the West Coast today will traverse the Northwest through Monday and then begin digging southeast out across the central/northern Plains by Tuesday where it will focus an area of low pressure. As this energy approaches the Midwest by Wednesday, there will be a secondary shortwave dropping southeast from southern Canada along with an attendant front that will attempt to phase with the lead energy. With the lead energy, the models are in good agreement until about 48 hours when the 12Z NAM and 00Z CMC begin to focus their low pressure over the Plains a little north of the 12Z GFS, 00Z UKMET and 00Z ECMWF. By Wednesday though, the CMC ends up with a bit stronger low pressure over southern MN. Regarding the secondary shortwave, the NAM and CMC are the weakest solutions, with the UKMET the strongest. The GFS and ECMWF are clustered in between only modest timing differences seen among the models with this energy. Will suggest a blend of the GFS and ECMWF with both shortwave impulses given their good clustering and ensemble support. ...Upper level trough approaching the West Coast by Tuesday... ...Accompanying offshore surface low... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Average The models are in generally good agreement with the timing and overall depth of the system as it comes across the West Coast late Tuesday and pivots northeast across the Pacific Northwest on Wednesday. The 12Z NAM though toward the end of the period does tend to be a little more aggressive with the height falls pushing toward southern British Columbia. Will recommend a non-NAM blend at this stage, ...Lingering upper level trough over the Southeast from Monday through Tuesday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC blend Confidence: Slightly above average Models show similarity with this system, with the exception of the 00Z CMC which does not lift the trough out of the Southeast from Tuesday into Wednesday as the other models do. Also, the CMC is an outlier solution with its deepening surface low off the East Coast Tuesday and Wednesday. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison