Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1244 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/00Z 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 00Z ECMWF along with support from the 06Z 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: Blend of the 12Z GFS/00Z UKMET and 00Z CMC 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 12Z NAM and 00Z ECMWF maintain a closed low feature farther west back over western AZ/southeast CA by Saturday evening, whereas the 12Z GFS, 00Z UKMET and 00Z CMC favor a bit more advancement downstream toward NM and possibly west TX. For now will lean toward the slightly more progressive camp, given a better ensemble clustering away from the NAM/ECMWF solutions. Thus, will prefer a blend of the 12Z GFS, 00Z UKMET and 00Z CMC. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison