Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1241 AM EDT Mon Jul 6 2020 Valid Jul 6/0000 UTC thru Jul 9/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Trough building over the Northeast U.S. this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: GFS/ECMWF/UKMET Confidence: Slightly above average Northwest flow shortwave trough energy will move across the Northeast and New England Monday, and is quickly replaced by brief ridging for Tuesday. By mid-week, a broad shortwave trough crosses northern New England. Overall, model guidance is fairly agreeable through the period with some minor model differences noted, with the NAM faster and the CMC not as strong with the mid-week trough. Blending the GFS/ECMWF/UKMET should serve as a good starting point. Trough/weakness over the Gulf Coast region ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Average Broad weakness in the larger scale upper ridge over the Southeast and Deep South will remain in place over the next several days with some suggestion in the latest guidance of more organized shortwave energy near the Southeast coast by mid-week. Model guidance has consolidated better over the last couple of cycles and largely agree on the evolution through Wednesday night. The main exception is the UKMET, which shows a faster progression of the weakness/energy off the Southeast coast compared to the rest of the deterministic guidance, and continues to indicate a stronger ridge over the central U.S. Therefore, a non-UKMET blend is still preferred. Trough with multiple shortwaves across the Pacific Northwest and Canada ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: ECMWF/CMC/EC mean blend Confidence: Slightly above average Within the broad trough over the Pacific Northwest, a stronger shortwave trough approaches the coast late Monday into Tuesday. Aside from a slightly deeper NAM, model agreement is very good with this system. Eventually the energy works across the northern Rockies and is forecast to close off over the southern Canadian Rockies. The GFS is initially quicker here, but becomes well clustered with the other guidance by the end of the forecast period. The NAM becomes slower with the closed low across south-central Canada by mid-week. With the next system arriving towards the end of the forecast period, the NAM and GFS are more potent by developing a closed low by Wednesday night, whereas the non-NCEP guidance suggests more of an open trough. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick