Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1151 AM EST Fri Mar 02 2018 Valid Mar 02/1200 UTC thru Mar 06/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation...along with model preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Powerful nor'easter impacting the Mid-Atlantic/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement in taking the strong nor'easter currently impacting the Mid-Atlantic and Northeast off to the east and out to see over the next 24 to 36 hours. A general model blend will be preferred at this time given good model mass field clustering. ...Deep closed low impacting the Western U.S. through Saturday... ...Negatively tilted trough approaching the Plains on Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 60 hours Blend of the 12Z GFS and 00Z UKMET...after 60 hours Confidence: Slightly above average The models all take a strong closed low offshore the Pacific Northwest today gradually south which broadens out over the next day and then moves inland across the Intermountain region. This will allow a broad trough to envelope all of the West through Sunday. The guidance though indicates that energy lifting out of the base of the trough by late Sunday will allow the trough to take on a negative tilt out across the central/northern Plains through Monday before then closing off in the mid levels. Surface low pressure over the Great Basin through Sunday is expected to reorganize over the Plains on Monday and begin lifting toward the upper Midwest. The guidance is generally in good agreement with their timing and depth of the trough evolution through early Monday, but by the end of the period, the 00Z ECMWF and the 00Z ECENS mean both support the closed low lifting farther north than the model consensus. The 00Z CMC appears to be too weak, and a bit too progressive. The 12Z NAM, 12Z GFS and 00Z UKMET should very good agreement with respect to timing and also generally with the depth of the height falls, but by the end of the period the NAM appears to be too weak at the surface. The better model clustering as a result suggests leaning toward a blend of the GFS and UKMET, which will be the preference after 60 hours. A general model blend will be preferred prior to this. ...Trough digging southeast across the Northeast on Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS and 00Z ECMWF Confidence: Average The models take a portion of the trough/closed low just southwest of Hudson Bay and slowly shift it southeast across Quebec on Sunday and then in more of sheared fashion down across the Northeast on Monday as the system encounters a blocking high that is settling southwest from southern Greenland. Not every model shears all of the energy down across the Northeast though as the 12Z NAM, 12Z GFS, 00Z ECMWF and the 00Z CMC keep a sizable degree of their energy up across southeast Canada to the west of the blocking ridge. The 00Z UKMET was more emphatic on bringing more energy farther southeast across the Northeast. Regarding the best model clustering, the GFS and ECMWF are the closest and have support from the latest GEFS mean. Will favor a blend of the GFS and ECMWF at this time as a result. Previous model trends at www.wpc.ncep.noaa.gov/html/model2.shtml Previous 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison