Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 247 PM EDT Sat Mar 28 2020 Valid Mar 28/1200 UTC thru Apr 1/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 19Z Update: The 12Z CMC remains more amplified than the model consensus with the trough crossing the southern tier states, and then becomes slower by the end of the forecast period Tuesday evening. With the arrival of the latest UKMET, CMC, and ECMWF, the NAM is now the most progressive solution across the Deep South and the UKMET is now a part of the preferred model blend here. The UKMET has also trended closer to the consensus with the front approaching the Pacific Northwest. Upper Midwest to East Coast storm system ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM consensus after 12Z Monday Confidence: High The closed low currently over the central Plains will continue tracking towards the Great Lakes region by Sunday afternoon, and then reach New England by Monday night. Secondary cyclogenesis is forecast near the Northeast Coast by Monday morning. The models are in good agreement through Monday morning, after which the 12Z NAM becomes slower with the progression of the parent upper low and surface low across southern Ontario and New England, and also slightly weaker. The UKMET is slightly closer to the coast with the evolution of the coastal low, but still closer enough to be considered part of the model blend at this time. Southwest shortwave spurring southern Plains cyclogenesis ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z UKMET/12Z GFS/12Z ECMWF Confidence: Moderate A shortwave trough currently near California will track eastward across the Desert Southwest and reach the central/southern Plains by Monday night. This will spur lee cyclogenesis over eastern New Mexico/Colorado and evolve into an organized storm system across the southern tier of the nation. The UKMET becomes slower as early as Monday morning across the Southwest, and this trend continues through the remainder of the forecast period. The CMC becomes more amplified by Monday night across the southern Plains and lies outside much of the ensemble spread. Although there are minor differences among the NAM, GFS, and ECMWF, there is enough overall agreement in these solutions to merit this blend as a starting point in the forecast process. Closed low and upper level trough approaching Pacific Northwest ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/12Z ECMWF/12Z UKMET Confidence: Moderate A broad upper level gyre dropping southeastward from the Gulf of Alaska will bring height falls to much of the northwestern U.S. by Monday morning. This will result in the passage of a cold front across the Pacific Northwest on Monday. The NAM is faster with the arrival of the height falls, and the UKMET is slightly slower with the arrival of the cold front. Confidence in the evolution is solid, but internal changes and run-to-run variations are likely to suggest confidence overall in the blend is average to slightly below average. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick