Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 143 AM EST Thu Dec 12 2019 Valid Dec 12/0000 UTC thru Dec 15/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00 UTC Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Southern Stream/Southeast to Mid Atlantic and Northeast surface low Fri-Sun... Preference: 00 UTC GFS/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 00 UTC GFS are faster to lift northward the main East Coast coastal plain low than yesterdays 12 UTC and todays 00 UTC ECMWF/UKMET and Canadian. The 18/00 UTC GEFS and 12 UTC ECMWF ensemble low clusters offer better support for the slower solutions. ...Northern Stream shortwaves across the Northern Plains to the Upper MS Valley and Upper Great Lakes... Preference: General 00 UTC 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/Canadian/UKMET/ECMWF Composite Confidence: Slightly below average A strong Day 1 surge of Pacifc energy into the Northwest seems pretty well defined in satellite and guidance, with blended precipitable water loops showing a long fetch moisture connection into the tropical Pacific. The inland progression of subsequent Pacific system energy farther south into CA and the Southwest over the weekend leads to differences with the 00 UTC ECMWF and 12 UTC ECMWF ensembles uncharacteristically showing faster progression than most other guidance. The 00 UTC GFS/Canadian/UKMET trend for increased amplitude and slower progression may be reasonable given upstream mid-upper level ridge amplitude, but suggest holding onto some blend input from the 00 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