Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1133 AM EST Fri Dec 13 2019 Valid Dec 13/1200 UTC thru Dec 17/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Evaluation with Preliminary Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Eastern 2/3 of the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non-NAM blend Confidence: Slightly above average A couple of systems will work through the eastern 1/3 CONUS over the next 3 days. In the near term, a wave of low pressure and associated mid/upper level trough will lift through the East Coast, bringing widespread precipitation to much of the region. An area of low pressure will move from near the Gulf Coast toward the Mid-Atlantic and then deepen over the Northeast. There is above average agreement with the placement, strength, and track of low through 60 hours. A secondary system will develop later in the forecast period, as shortwave energy from the west coast reaches the southern/central Plains. A low pressure is forecast to develop in the vicinity of north Texas and then lift east/northeast toward the Ohio Valley by 84 hours. Here, the 12Z NAM mass fields (particularly the surface low) is way ahead of the rest of the deterministic models (16.12Z low over CVG compared to the rest of the models which have a mean position of LIT). However, aloft, its 500 mb heights and vorticity is not substantially different and the resultant QPF is not too much of an outlier compared to the rest of the models. So, while the preference is lean away from the NAM, it is not necessarily considered an outlier. ...Western 1/3 of the CONUS.... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Shortwave trough moves onshore the western US Saturday and then will be followed by ridging anchored all the way through the west coast of Canada to end the forecast period (Monday). Overall model agreement is above average from the 500 mb heights to the surface as well as QPF fields. A general model 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