Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 146 AM EST Tue Jan 01 2019 Valid Jan 01/0000 UTC thru Jan 04/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z CMC blend Confidence: Average ...07Z update... The 00Z CMC stands out the most from the other models with most systems impacting the lower 48 but the UKMET from 00Z trended closer to the previously preferred consensus, led by the NAM, GFS and ECMWF. The 00Z ECMWF adjusted a little south and slower with the track of the southern stream closed low as it nears the lower Mississippi Valley, between the 00Z NAM and 00Z GFS, with the 00Z UKMET just ahead of the 00Z NAM. Essentially, a non 00Z CMC blend is reasonably close to the latest GEFS/ECMWF ensemble mean positions. Across the Northwest, generally good agreement exists outside of the faster 00Z CMC with an non 00Z CMC blend appearing best there. ...previous discussion follows... After the departure of a deepening surface low and accompanying mid-level shortwave from off of New England today, two significant shortwave troughs remain across the lower 48, one in the form of a closed low over the Four Corners region and the other a southward amplifying shortwave through in south-central Canada. There is strong ensemble agreement that these two features do not phase but there are still some timing and placement differences with the southern stream system across the lower Mississippi Valley. Lastly, a progressive shortwave trough is expected to reach the Pacific Northwest coast Thursday night. Ensemble and deterministic trends with the closed low tracking into the southern Plains continue to show some slight slowing compared to yesterday but spread continues to shrink and there is relatively good agreement. However, the 12Z UKMET/CMC are faster than a preferred blend of the GEFS/ECMWF ensemble means. The 00Z NAM, 00Z GFS and 12Z ECMWF show decent agreement with the ensemble means and one another but the 00Z GFS ends up a bit farther south than the ensemble mean position near the lower Mississippi Valley Thursday night, so a blend closer to the 00Z NAM and 12Z ECMWF is preferred with less GFS weight. The northern stream shortwave track through the Great Lakes Wednesday night has good support from the 00Z NAM/GFS and 12Z ECMWF with average spread remaining in the latest ensembles. Across the Pacific Northwest, the 12Z CMC stands out toward the faster side of the latest ensemble members with much stronger support for a slower track near the 00Z NAM/GFS and 12Z ECMWF with the 12Z UKMET a bit on the faster side. Between the NAM/GFS/ECMWF, the NAM is a bit slower and south with the surface low offshore Thursday night, with better ensemble support for a 00Z GFS/12Z ECMWF blend. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto