Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1227 PM EDT Sun Jul 05 2020 Valid Jul 05/1200 UTC thru Jul 09/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Trough building over the Northeast U.S. this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend 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, there are hints of a weak shortwave trough skirting portions of northern New England. Overall, model guidance is fairly agreeable through the period with some minor speed differences noted, where the GFS is a touch faster and the UKMET slower. The CMC has higher heights at 500 mb and is a bit flatter in general, but all together, the differences don't preclude going with a general model blend at this time. 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 off the GA/SC coast by mid-week. Model guidance has consolidated better over the last couple of cycles and largely agree on the evolution through 84 hours. 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. For this reason, a non-UKMET blend is still preferred. Trough with multiple shortwaves across the Pacific Northwest and Canada ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Slightly above average Within the broad trough over the Pacific Northwest, a stronger shortwave trough approaches WA/OR late Monday into Tuesday. Aside from a slightly deeper GFS/NAM, model agreement is very good with this system. Eventually the energy works through the northern Rockies and is forecast to close off over the southern Canadian Rockies. The CMC is flatter/open the most and doesn't suggest a closed low forms while the ECMWF is displaced to the west compared to the nearly identical GFS/UKMET position. The NAM does eventually develop the closed low, but is 6-12 hours later. Finally, another system will then approach the Pacific Northwest mid-week. Here, the UKMET is slower and but the rest of the guidance shows good clustering. For these reasons, a non-UKMET blend is preferred for this region. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor