Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 237 PM EDT Fri Apr 03 2020 Valid Apr 03/1200 UTC thru Apr 07/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 05.12Z; GFS/ECMWF blend after Confidence: Average 19Z update: The rest of the 12Z guidance (ECMWF/UKMET/CMC) showed no significant differences or deviations from the earlier guidance over the next 3 days for the mass fields to warrant a change in the previous blend preference. Fairly good agreement in the large scale pattern across the CONUS. ---previous discussion--- Large scale synoptic pattern across the CONUS currently features large gyre over Alberta while the offshore Northeast U.S. system begins to pull away. Over the coming 2-3 days, several impulses will work through that large system over the northern Rockies. Meanwhile, eastern Pacific energy will evolve into a large closed low off the California coast by the end of the forecast period. Finally, weak southern stream energy will move through the southern Plains, Texas Gulf Coast region and be the focus for locally heavy rainfall potentially. Overall, models show fairly good agreement with the 500 mb pattern over the next 3 days across the CONUS. This includes the several pieces of energy rotating the base of the large closed low over Alberta. For the leading shortwave over the northern Plains, the latest 12Z guidance shows very good agreement. Differences in the southern stream energy across Texas are more tied to mesoscale features and ingredients but the significant moisture/instability return does present the potential for heavy rainfall/flash flooding. But overall the 12Z mass fields are in good shape such that a general model blend is preferred. Finally, over the western U.S., a pair of shortwaves off the Pacific NW coast will gradually evolve into a large closed low by day 3. For the initial shortwave, a general model blend is sufficient. As the secondary, larger shortwave moves into the area and closes off, there remains some latitudinal spread in the latest guidance. Over the last several model cycles, the GFS/ECMWF remain the more consistent and middle ground approach and for this cycle, a blend of the two deterministic runs are preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor