Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 244 PM EDT Wed Mar 13 2019 Valid Mar 13/1200 UTC thru Mar 17/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Powerful deep closed low impacting the Plains/Midwest... ...Secondary shortwave digging across the Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...led by the 12Z GFS/ECMWF Confidence: Above average The models show very good agreement in taking the deep layer closed low off to northeast across the central Plains through tonight and then across the Upper Midwest through Thursday. This energy will then eject across the Great Lakes and southeast Ontario by Friday as a trailing cold front sweeps through the eastern U.S. and then offshore the East Coast by Saturday. In behind the departing Midwest storm system will be a new northern stream trough for which the 12Z NAM is a bit stronger than the model consensus. While the large scale differences are quite modest with respect to the exiting surface low/height falls, and with the timing of the surface cold front sweeping across the East, the overall better model clustering is with the 12Z GFS and 12Z ECMWF along with support from the 12Z GEFS mean and 00Z ECENS mean. Will prefer a general model blend weighted toward the GFS/ECMWF solutions as a result. ...Weak upper trough reaching the West Coast Thurs night... ...Digging into the Southwest on Fri/Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-GFS blend Confidence: Average A weak upper trough will approach the West Coast by Thursday night and then separate out from the westerlies and dig into the Southwest on Friday and Saturday. The guidance agrees in developing a weak closed low feature over AZ by early Saturday, and then differences appear with how quickly this energy advances east toward the southern High Plains. The non-NCEP models led by the 12Z UKMET/12Z CMC and 12Z UKMET have all clustered together on a slower evolution of the closed low as ridging develops farther north over the Great Basin. The 12Z NAM agrees with the non-NCEP cluster, and it would appear at this point that the 12Z GFS is a bit of a progressive outlier. The 12Z GEFS mean trended slower and is farther west with the troughing/closed low by the end of the period. The 00Z ECENS mean already strongly supports the slower camp, and so based on the latest model trends and clustering, a non-GFS consensus will be preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison