Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 141 PM EST Sat Jan 11 2020 Valid Jan 11/1200 UTC thru Jan 15/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Final Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/12Z ECMWF blend Confidence: Slightly above average ...19Z update... The 12Z UKMET sped up relative to its previous 00Z cycle with the exiting East Coast system on Sunday and the weak system approaching the Great Lakes early Monday. Outside of this change in the UKMET, only minor changes were noted with the 12Z ECMWF/UKMET/CMC relative to their previous 00Z cycles. There was some convergence with the amplitude of the western trough for Tuesday, but timing differences increased slightly. A 12Z GFS/ECMWF blend still looks representative of the middle of the model spread for the CONUS. ...previous discussion follows... A powerful mid-level trough over the Southern Plains this morning is forecast to track northeastward atop an anomalous ridge centered just off of the East Coast. The accompanying surface cyclone will quickly track from the Ohio Valley across New England with good model agreement. However, the 00Z UKMET was slightly slower to exit the cyclone eastward relative to the remaining available deterministic/ensemble guidance. After the departure of the system crossing the Northeast early Sunday, the upper level pattern will feature a broad trough centered over the western 2/3 of the nation with the aforementioned ridge over the western Atlantic. A series of shortwaves will track across the western U.S. into the Great Plains followed by weakening toward the Great Lakes. The western portion of the front exiting the East Coast on Sunday will be left draped from Ensemble agreement is fair to good for the short range period (ending Tuesday evening) with the overall preference to be near the middle or 00Z ECMWF mean given consistency from run to run and its positioning toward the middle of the latest deterministic/ensemble spread. The 00Z UKMET was noted to be slightly slower than ideal with the first of the shortwaves expected to reach the Great Lakes region late Sunday night/early Monday morning. Regarding the second shortwave, model consensus shows the 12Z GFS to be a little slow as a surface low nears the Great Lakes on Tuesday, with the 12Z NAM and 00Z ECMWF in better alignment with the model consensus. However, the 12Z NAM develops timing issues with a system upstream which impacts the flow downstream over the eastern half of the nation. A transition toward a 12Z GFS/00Z ECMWF blend is recommended from Monday night into Tuesday. The last shortwave to mention for the short range will reach the West Coast Tuesday morning. Outside of the much flatter 12Z NAM, amplitude differences show the 12Z GFS/00Z UKMET flatter compared to the deeper 00Z ECMWF/CMC. A blend toward the middle (12Z GFS/00Z ECMWF) is recommended here and will work for most of the remainder of the CONUS through Tuesday evening. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto