Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1240 PM EDT Wed Jun 26 2019 Valid Jun 26/1200 UTC thru Jun 30/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Final Confidence and Preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exceptions: 00z UKMET/ECMWF and 12z GFS in Northwest late Sat/Sun 12z GFS/ECMWF/CMC across Northern Plains/Great Lakes Thur/Fri Non-ECMWF blend Northeast Sunday Confidence: Average Large scale pattern depicts a strong closed low off the Pacific Northwest coast with broad southwesterly flow across the Rockies over a building ridge in the Central Plains. The flow then becomes broadly zonal across the northern third of the US with a westward shifting Subtropical Atlantic ridge nosing toward the Sargasso Sea. Guidance is fairly agreeable up until the weekend as the Pacific closed low starts to break down and shift northeast into Alberta with a lingering trof or weaker closed low remaining across the Pacific Northwest by the end of the forecast period. The differences across the Northwest are dependent on the strength/magnitude of the binary interaction of the deepening wave in Canada pulling the remainder north, though there is a trend toward greater agreement. The NAM/GFS both suggest stronger Canada waves drawing the energy north, but the GFS being faster with the Gulf of AK energy, lead to a further southwest stretching of the trof. The 00z CMC is very similar to the NAM though the ECMWF/UKMET are most middle ground. The differences in QPF are fairly limited given the orientation of the onshore flow is similar/agreed upon even if the remaining vorticity centers aloft are more strung out. Still, would favor the ECMWF/UKMET and GFS (matching the ensemble suite and trends). The strength/placement of the Central High Plains ridge, extends up to the Red River of the North River Valley and is strongly agreed with only the GFS a bit east compared to the remaining guidance. The weakness between the ridge centers (Central High Plains and off Carolina Coasts) will see increased northward return of MCVs/shortwave energy that will link up with easterly tropical wave/TUTT cell across the North Central Gulf. There is solid model agreement for this feature as well supporting general model blend. Further east across the Great Lakes into New England, the zonal pattern breaks a bit as a fast moving shortwave out of the southwesterly flow develops across the Dakotas Thursday evening and rapidly shifts eastward. There remains a modest spread in latitude with this wave and the NAM/UKMET both continue to be stronger supporting a weak surface depression much closer (northward) to the larger scale closed low in Canada, while the GFS/ECMWF/CMC remain a bit weaker further south which remains more favored overall. Toward the weekend, the exiting shortwave will aid the development of a digging trof (given the upstream ridge building), there is some moderate disagreement in how the wave/closed low drops south out of central Canada toward SE Canada affecting the lower Great Lakes into the Northeast by Sunday. The ECMWF is initially slow with the exiting wave which actually leads to increased binary iteration/shearing of the closed low eastward. In doing so, the remaining core of the close low drops south faster and further west than the remaining guidance that is retains a more full bodied/concentric closed low, making the ECMWF a bit less favorable across this region toward the end of the forecast period. The 12z GFS remains the most concentric with the wave and is therefore a bit slower than the NAM/CMC and is more in-line with ensemble suite/trends and should be weighted a bit higher in the blend through the weekend here. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina