Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1139 PM EST Fri Dec 07 2018 Valid Dec 08/0000 UTC thru Dec 11/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Pattern across South Central US/Southeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z ECMWF/ECENS; 12z UKMET; 00z GFS/NAM Confidence: Average A wave of low pressure will develop across the northern Gulf and move up the southeast US coast before departing off Cape Hatteras. There is increasing consensus with the low track and speed, though the 00z GFS is still a faster solution, but overall the spread is much less compared to 24 hours ago. For thermal profiles, the NAM is again warmer aloft in the mid levels, eroding the cold air wedge from GA to SC/NC faster compared to the rest of the guidance. QPF differences are seen in the lingering deformation band snow across western and central NC Sunday into Sunday evening. The GFS is quick to pull out of the area, resulting in less QPF. Meanwhile, the rest of the guidance shows an axis of heavier QPF generally in the same area. The ECMWF is bit further south compared to the CMC/UKMET. For this cycle, the WPC preference is leaned on the 12z ECMWF/ECENS with some weight given to the UKMET/GFS/NAM. ...Pacific Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non-NAM Confidence: Slightly above average The western ridge begins to break down tonight as a lead shortwave trough pushes onshore along with a surface cold front. This is well represented by the current models. After a short break, a more pronounced shortwave trough will push onshore Sunday night into Monday night. This is where there are considerable differences in the synoptic fields. The 00z NAM digs the trough the deepest, well into southern CA, and is more neutrally tilted. Meanwhile, most of the other available guidance (00z GFS, 12z UKMET, 12z ECMWF, 12z CMC) are more positively tilted with the trough axis. At the surface, the NAM is significantly stronger and faster with a low across the Gulf of Alaska and bringing the cold front onshore. At this time, a non-NAM blend is preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor