Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 103 AM EDT Sun Mar 29 2020 Valid Mar 29/0000 UTC thru Apr 01/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z NAM/GFS Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low weakening from the Upper Midwest to the Northeast through Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model compromise Confidence: Above average Only minor timing/thermal/strength differences remain with this system as the powerful closed low over the Upper Midwest on Sunday morning, weakens toward the Northeast for Monday and Tuesday. As a secondary low develops in the guidance Sunday night near the New England coast, minor placement differences develop with perhaps the 12Z UKMET closest to the coast, but overall differences in the latest deterministic and ensemble guidance are minor. ...Southwest shortwave spurring southern Plains cyclogenesis early in the week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 75% 12Z ECMWF, 25% 00Z NAM blend Confidence: Average Some timing differences develop early with the shortwave trough across the Southwest. The 00Z NAM ends up faster than most of the guidance through Monday while the 12Z UKMET/CMC end up slower. While the slower/farther south track of the 12Z UKMET/CMC's shortwave continues through Wednesday morning, the 00Z NAM timing slows more in line with the best ensemble clustering while the 00Z GFS pulls ahead. The 12Z ECMWF is considered the best model for this system with the 00Z NAM second best but the 00Z NAM is a bit stronger, colder and north than the remaining guidance. Closed low and upper level trough approaching Pacific Northwest ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z ECMWF/12Z UKMET blend Confidence: Average While the 00Z GFS ends up slower with the timing of the lead shortwave trough moving across the U.S./Canadian border Monday night into Tuesday, located on the front edge of a longwave trough overtaking the Northwest, when the 00Z GFS is combined with the 12Z ECMWF and 12Z UKMET, a reasonable blend is reached. The 00Z NAM is considered too amplified with heights into the Intermountain West, while the 12Z CMC is flatter/weaker with the overall longwave trough. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto