Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 236 PM EST Wed Dec 05 2018 Valid Dec 05/1200 UTC thru Dec 09/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend, less weight to 12Z GFS/UKMET Confidence: Slightly Above average A positively tilted trough off California today will shift southeast to northern Mexico through Friday and reach the southern Great Plains Saturday. Little precipitation is expected with this system in the CONUS until Friday when Gulf moisture is tapped over TX. Precipitation then blossoms over the southern Plains and lower MS Valley through Saturday as surface low pressure develops with heavy rain threats near the Gulf Coast and wintry weather threats inland on the north side of the precipitation shield. Good agreement is seen among global guidance with the trough position and depth until Saturday when timing and magnitude differences become apparent. There are essentially two camps in the 12Z guidance in terms of timing and magnitude. The 12Z GFS and UKMET are progressive and less deep than the slower 12Z NAM/ECMWF/CMC/FV3 consensus. Differences between these two camps is not that great and is best displayed in Day 3 QPF. Given only two more open and progressive solutions, the preference is for the 12Z NAM/ECMWF/CMC/FV3 with minor inclusion of the 12Z GFS/UKMET. There has been a trend to a blend of both camps; notably a more progressive 12Z ECMWF over the previous run and a continued slowing trend in the GFS. The other area of notable precipitation in the CONUS in the 3-day forecast range is with a trough approaching the coastal Pac NW Saturday. The 12Z ECMWF has a stronger downstream ridge, but there is little impact in QPF compared to consensus, so a general model blend is warranted there. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Jackson