Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 145 PM EST Tue Jan 14 2020 Valid Jan 14/1200 UTC thru Jan 18/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave crossing the Great Lakes/Northeast through Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The low-amplitude shortwave impulse currently moving into the Great Lakes region will cross the Northeast on Wednesday. The guidance is in very good agreement with this system, so a general model blend will be preferred. ...Shortwave currently over the Northwest... ...Crossing the Upper Midwest/Northeast through Wed/Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS/CMC/ECMWF Confidence: Slightly above average The shortwave trough moving across the Northwest around the base of the deep upper low over southwest Canada will eject quickly east across the northern Plains and Upper Midwest through Wednesday, and then amplify into the Northeast on Thursday. Surface low pressure associated with this system will cross the Midwest and advance through New York and New England early Thursday before deepening over the Gulf of Maine by midday Thursday. The guidance is in good agreement until it arrives across the Northeast where the 12Z NAM begins to edge a tad stronger than the global models with the upper trough, and also tends to tuck the surface low in a little closer to eastern Maine. There is a little bit of latitudinal spread seen with the global models as the 12Z non-NCEP guidance is a tad south of the NAM and GFS solutions. The 12Z UKMET is overall the farthest south as the low ejects through the Gulf of Maine. Accounting for the NAM and UKMET solutions, the preference will be toward a blend of the GFS, CMC and ECMWF at this time which is reasonably well supported by the latest GEFS/ECENS means. ...Deep upper trough crossing into the West by Thurs... ...Ejecting out across the Plains/Midwest late Fri... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z ECMWF/GEFS and 00Z ECENS Confidence: Slightly above average The guidance brings a strong deep layer trough into the West by Thursday with the height falls and an area of leeside cyclogenesis then ejecting out across the Plains and Midwest on Friday. The 12Z GFS is on the faster side of the guidance by late Friday with the 12Z NAM the slowest. The NAM also is appearing to be a bit too deep with the northern portion of the trough as it ejects across the northern Plains. Generally, the 12Z non-NCEP models split the difference. The 12Z ECMWF appears to best approximate the model consensus, and has good support from the latest GEFS/ECENS suites. A blend of the ECMWF and ensemble means 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