Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1239 PM EDT Mon Mar 11 2019 Valid Mar 11/1200 UTC thru Mar 15/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper trough departing from the Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Only minor differences remain with this system, with a general model blend recommended to smooth out any smaller scale discrepancies. ...Upper trough crossing the Pacific Northwest Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement in bringing a progressive northern stream trough in across the Pacific Northwest on Tuesday before then digging into the Intermountain West where it will begin to interact with a large southern stream closed low ejecting out of the Southwest. A general model blend will be preferred with this system as it advances into the Intermountain West. ...Large closed low crossing the Southwest Monday/Tuesday... ...Phasing with digging northern stream trough... ...Associated deep surface low over the Plains/Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/GFS and 00Z ECMWF blend...thru 60 hrs 12Z GFS/00Z ECMWF blend...after 60 hrs Confidence: Slightly above average A large deep layered closed low just offshore of southern CA will move east across the Southwest through Tuesday and then eject northeast out across the central Plains Wednesday where strong lee-side cyclogenesis will take place. The guidance agrees in showing strong phasing of this energy with the aforementioned northern stream trough digging across the Intermountain West. This will result in a very strong surface low moving from southeast CO through western/central KS on Wednesday and then northeast across IA by Thursday. The 00Z CMC and 00Z UKMET are a little weaker than the overall model consensus with the height falls, at least through Wednesday which results in a modestly weaker surface low. The 12Z NAM/GFS and 00Z ECMWF along with a substantial number of ensemble members favor a stronger/deeper evolution given the degree of phasing over the High Plains. There is some latitudinal differences noted as well as the 00Z ECMWF/ECENS mean both support a low track a tad north of the multi-model consensus, and the it was noted that the NAM/GFS solutions both slowed their low tracks down a little compared to their 00Z runs. For now, will prefer a blend of the 12Z NAM/GFS and 00Z ECMWF through 60 hours, and then a 12Z GFS/00Z ECMWF blend thereafter as the NAM begins to more substantially lag the global models with the height fall evolution. ...Upper trough approaching CA by Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/GFS and 00Z ECMWF blend Confidence: Slightly above average The models bring another shortwave trough toward CA on Thursday. The 00Z UKMET is the slowest solution, with the 00Z CMC the fastest. The 12Z NAM/GFS and 00Z ECMWF all split the difference in between, but the NAM is the slower solution of this camp. Will prefer a 12Z NAM/GFS and 00Z ECMWF blend at this point given better ensemble support. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison