Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1259 PM EDT Sat Mar 14 2020 Valid Mar 14/1200 UTC thru Mar 18/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Final Model Evaluation with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overview of systems affecting the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The upper pattern across the lower 48 will be quasi-amplified in the short range with highly meridional flow along the west coast of North America and zonal flow over the eastern 2/3 of the nation...at least early on. By Monday, a longwave trough will begin to sweep across the north-central U.S./Great Lakes region into the middle of the week. There were some minor differences with a strong closed low dropping south along the West Coast with the 12Z NAM/GFS stronger with the 850-500 mb low compared to the 00Z ECMWF/UKMET/CMC. The ensemble means split the difference in strength. By Monday evening, minor timing differences arise with the 12Z NAM fastest with a lobe of energy into the Southwest, bringing the closed low to the east faster than a strong majority of guidance. However by Tuesday evening, the differences in timing are reduced and so a general model blend appears reasonable for this system with perhaps less 12Z NAM influence Monday into Tuesday. Up north, the 12Z GFS continues to be slightly faster with a longwave trough and associated cold front through the northern U.S. The 00Z ECMWF/UKMET catch up with the 12Z GFS by later Monday though with perhaps the 12Z NAM and 00Z CMC looking a bit slow. The differences in timing are more of an impact to Ontario and Quebec with resulting impacts across the U.S. relatively minor. Other systems affecting the lower 48, including a weakening shortwave across the Mississippi River Valley today and a frontal boundary across the southern U.S. show rather good agreement with model mass fields, supporting a general model blend. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto