Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1220 PM EDT Sat Jul 14 2018 Valid Jul 14/1200 UTC thru Jul 18/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Model Analysis for the CONUS... Overall Preference: Blend of 12Z GFS and 00Z ECMWF General Confidence: Slightly above average The pattern over the CONUS this weekend will be generally dominated by high pressure aloft and weak flow, with one center over the Four Corners region and another one extending from the OH/TN Valleys south down across the Gulf Coast states. A broad weakness between the two upper level high centers is expected to remain over the central Plains and adjacent areas of the Midwest through Sunday. However, the large scale pattern will change going into early next week as a trough will be digging across the Upper Midwest, Great Lakes and Northeast which will drive a cold front across the Midwest and toward the Eastern Seaboard by Tuesday. The guidance is in good agreement with this scenario, but the 12Z NAM was seen as being a little sharper than the global models with the height falls across the Great Lakes and OH Valley. By Monday and Tuesday, there will be two troughs also impacting the Northwest with one system crossing the Pacific Northwest and the northern Rockies by Tuesday. The 12Z GFS and 00Z ECMWF cluster very well with this system and are seen being a little more progressive than the 00Z CMC/UKMET and 12Z NAM, with the NAM overall the strongest solution. Meanwhile, a second trough will begin to impact the Pacific Northwest by Tuesday evening. The 12Z NAM is the fastest solution with this second system, and the 00Z CMC the slowest. There is very good model timing and depth agreement in general with the 12Z GFS, 00Z ECMWF and to some extent the 00Z UKMET with this next trough. Based on the good overall model clustering seen with the GFS and ECMWF across the CONUS, a blend of the GFS and ECMWF will be preferred at this time with the shortwave troughs and larger scale pattern. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison