Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1158 PM EST Wed Dec 11 2019 Valid Dec 12/0000 UTC thru Dec 15/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Southern Stream/Southeast to Mid Atlantic and Northeast surface low Fri-Sun... Preference: 00 UTC GFS and 12 UTC ECMWF/UKMET/Canadian Blend Confidence: Average Details with upper support/impulses seem small scale and noisy, with larger guidance variance more evident with surface based system progressions/QPF into the weekend. The 00 UTC NAM and to a lesser extent the 12 UTC GFS are faster to lift northward the main East Coast coastal plain low than the 12 UTC ECMWF, UKMET, and Canadian. The latest 18 UTC GEFS and 12 UTC ECMWF ensemble low clusters offer better support for the slower solutions, but it will be interesting if the 00 UTC ensembles speed up given the fast upstream/pos-tilt flow driving flow aloft and small wavelength spacing between impulses. ...Northern Stream shortwaves across the Northern Plains to the Upper MS Valley and Upper Great Lakes... Preference: General Model Blend Confidence: Average Prefer a general model blend with reasonably well clustered model and ensemble solutions despite fast flow with numerous embedded smaller scale impusles and some weekend stream interactions. A composite seems reasonable and offers decent continuity given complexity. ...West/Rockies/Plains... Preference: 00 UTC GFS and 12 UTC ECMWF Composite with more weighting on the GFS Confidence: Slightly below average A strong Day 1 surge of Pacifc energy breaching the Northwest Coast seems pretty well defined in satellite and guidance, with latest blended TPW loops showing a long fetch moisture connection into the tropical Pacific. The inland progression of addional Pacific system energy into CA and the Southwest over the weekend leads to more pronounced surface differences with the 12 UTC ECMWF/Canadian/UKMET and ECMWF ensembles showing faster progression over the West and quicker to develop southern high plains cyclogenesis and post-frontal high pressure spillage than the 00 UTC GFS/NAM and 18 UTC GEFS. At this point, the 00 GFTS UTC trend for more amplitude/less progression may be reasonable given upstream mid-upper level ridge amplitude, but suggest holding onto some blend with the 12 UTC ECMWF considering forecast spread/uncertainty. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Schichtel