Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 257 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/ECMWF blend...thru 72 hrs 12Z GFS/ECMWF blend...after 72 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 12Z CMC and 12Z UKMET are still 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/ECMWF solutions along with a substantial number of ensemble members favor a stronger/deeper evolution given the degree of phasing over the High Plains. The latest ECMWF did slow its low track down a bit and is a little farther south to put it into better agreement with the NAM/GFS camp at least through 72 hours. After 72 hours, the NAM begins to lag the multi-model consensus a bit with the timing of the wave, and UKMET begins to shift its closed low a bit north and a little faster than the model consensus. Will prefer a blend of the 12Z NAM/GFS/ECMWF solutions through 72 hours, and then a 12Z GFS/ECMWF blend thereafter. ...Upper trough approaching CA by Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/12Z GEFS mean/00Z ECENS mean blend Confidence: Slightly above average The models bring another shortwave trough toward CA on Thursday. The 12Z UKMET/ECMWF solutions are the slowest, with the 12Z GFS/CMC solutions the most progressive. The 12Z NAM is overall just a little faster than the UKMET and ECMWF. The latest 12Z GEFS mean and 00Z ECENS mean both favor a solution a little more progressive, and so will lean in this direction with a blend of the GFS and the GEFS/ECENS means. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison