Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1159 AM EST Sun Feb 03 2019 Valid Feb 03/1200 UTC thru Feb 07/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Model Evaluation...with Initial Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Low pressure off the Southeast and Mid-Atlantic Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/NAM/UKMET Confidence: Slightly Above Average A southern stream shortwave under the northern stream ridge shifts east over the southeast CONUS, closing off after 04/00Z over eastern NC. The 12Z NAM/GFS are now quite similar with both the mid-level low center and the surface low approaching the NC coast overnight. The 00Z ECMWF is displaced farther north and the 00Z CMC shifts the surface trough farther inland. Precipitation is quite similar from the 12Z NAM/GFS and not far off over land from the new 12Z UKMET, so these are preferred. ...Short wave and surface low Northern Rockies into the Upper Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/UKMET Confidence: Average Disagreements persist with timing and meridional placement of the shortwave trough crossing the northern Plains tonight into Monday with implications for wintry precipitation forecasts. The 00Z ECMWF is the slowest to progress the mid-level trough axis while the 12Z GFS and 00Z CMC are the most progressive and the 12Z NAM is the most amplified. The 12Z UKMET just came in and it is a good compromise among the global guidance. The western extent of precipitation over northern ND is in question with the slower ECMWF and stronger NAM having the quarter inch QPF across northern ND, much farther west than other guidance. The 12Z UKMET is a good compromise here with a nod to the western flank while also being similar across the Great Lakes to the global consensus. ...Closed mid-level low over CA/Great Basin... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z ECMWF/12Z NAM/UKMET blend Confidence: Average The low over Vancouver Island this morning is phasing with a shortwave low to its south which will draw the low along the WA/OR coast Monday and shift into northern CA Monday night. Timing of the opening of this low and progression of the positively tilted trough over the western CONUS through Wednesday begins to differ Tuesday night. The 12Z NAM and 00Z ECMWF remain the most positively tilted and slowest to eject east while the 12Z GFS remains the most progressive. Will continue to lean to the NAM/ECMWF blend given the strength of the closed low that the GFS seems too eager to eject. The 00Z CMC is nearly as progressive as the GFS while the 12Z UKMET is a compromise between the two camps. Will include some 12Z UKMET in the recommendation as a hedge toward ejection timing. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Jackson