Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 139 PM EST Wed Mar 04 2020 Valid Mar 04/1200 UTC thru Mar 08/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation with final preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Eastern half of the nation... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 12Z NAM, 12Z ECMWF and 12Z UKMET Confidence: Slightly above average Across the eastern U.S,, a surface low will track into the western Atlantic as a strong mid-level trough sweeps across the East Coast. The 00Z and 12Z CMC have been and continue to be slower with the upper trough, allowing for a more western surface low track offshore of the East Coast. The 12Z GFS appears a bit faster and north with the core of the upper trough that passes over the Great Lakes and Northeast. 12Z ECMWF/UKMET/CMC trends support a slightly slower upper trough progression and a more westward surface low track compared to their previous 00Z cycles. Ensemble support is greatest toward the middle of the latest spread, with decent run to run consistency supporting the middle ground or slightly west of the middle of the 00Z/04 ensemble cycle. A blend of the 12Z NAM, 12Z ECMWF and 12Z UKMET is preferred for the final preference, a slight westward shift compared to the previous preference. ...Western half of the nation... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average Across the western U.S., a longwave trough will approach the Pacific Northwest on Thursday along with an associated cold front. There are some minor differences within the base of the trough as it approaches northern California with the 12Z GFS and 00Z UKMET slower and more amplified with vorticity compared to the 12Z NAM, 00Z ECMWF and 00Z CMC. The differences are small enough and wash out as the feature moves inland, supporting a general model blend. Impactful differences were not observed for the 12Z ECMWF/UKMET/CMC compared to their previous 00Z cycles. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto