Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1220 PM EDT Thu Mar 19 2020 Valid Mar 19/1200 UTC thru Mar 23/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12z NAM/GFS Evaluation with Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low over the West... ...Low pressure crossing the Central Plains into the Upper Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The 12z NAM/GFS are close to the consensus spinning down the closed mid level low over CA/NV through 21/00z. Short wave energy ejected from the weakening mid low tracks across eastern CO, spinning up surface low pressure there before 20/00z. Once the surface low develops, there is generally good model agreement with the track and strength of the surface low as it crosses the central Plains and Upper Great Lakes before reaching Quebec around 20/12z. Given the good agreement with the track of the surface low, a general model blend is preferred, with slightly above average confidence. ...Mid level troughs affect the Northern Plains into the Upper Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z NAM/GFS/00z ECWMF blend Confidence: Average For the first short wave tracking out of central Manitoba, the 12z NAM/GFS are close to the consensus as it reaches the Upper Great lakes 22/00z. The 00z UKMET is slower than the consensus with this feature, though the trend for the UKMET has been faster with this feature. The 00z CMC is much deeper with the system, and has been trending in that direction. For the first short wave, a 12z GFS/NAM/00z ECWMF blend is preferred. For the second short wave tracking from Alberta into the Northern Plains by the end of the period, the 12z GFS is faster than the consensus, while the 00z UKMET/CMC remain slower with this feature. For the second short wave, the 12z NAM/00z ECMWF seem to form the best consensus, and are preferred with this feature. ...Mid level trough crossing Southwest Sat... ...Closed mid level low approaching Central/Southern CA Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z NAM/00z ECMWF blend Confidence: Average Short wave energy originating near 32N 133W at 20/12z tracks toward the Southern CA coast, reaching far Southern CA/northern Baja Peninsula at 21/12z. The 00z UKMET continues it trend of being the slowest member of the guidance envelope. For this feature, a blend of the 12z GFS/NAM/00z ECMWF is preferred. A closed mid level low near 34N 135W at 21/12z wobbles toward the Central and Southern CA coast by the end of the period (23/00z). With this feature, the 12z GFS begins to become faster than the consensus, and remains so through 23/00z. Outside of the 12z GFS, there is good model consensus with the track of the mid level low. For this feature, a non-12z GFS blend is preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hayes