MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1114 AM EST TUE DEC 23 2014 VALID DEC 23/1200 UTC THRU DEC 27/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SURFACE LOW WEAKENING ACROSS THE UPPER GREAT LAKES TUES NIGHT... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT DAMPENING OUT THE SURFACE LOW CENTER CURRENTLY OVER EASTERN IA THAT SHOULD MOVE ACROSS CENTRAL/EASTERN WI BY LATER TODAY. THE LOW SHOULD LOSE ITS IDENTITY TONIGHT IN LIEU OF THE STRONGER SHORTWAVE AMPLIFICATION OVER THE LOWER MS VALLEY AND ASSOCIATED SURFACE CYCLOGENESIS. ...INTENSIFYING LOW LIFTING ACROSS THE TN/OH VALLEYS AND GREAT LAKES ON WED... PREFERENCE: BLEND OF THE 00Z ECMWF AND 00Z GEM CONFIDENCE: AVERAGE THE 12Z NAM IS A LITTLE SLOWER THAN THE MULTI-MODEL CONSENSUS WITH THE INTENSIFYING SURFACE LOW THAT LIFTS NORTH-NORTHEAST ACROSS THE TN/OH VALLEYS AND THROUGH THE GREAT LAKES REGION...WITH THE BIGGEST TIMING DIFFS NOTED AS THE LOW CROSSES LOWER MI WED NIGHT. THE 12Z GFS AND 00Z UKMET ARE A BIT FASTER THAN THE MULTI-MODEL CONSENSUS. THE 00Z ECMWF AND 00Z GEM SPLIT THE DIFF WITH TIMING. OVERALL...THE MODELS TEND TO AGREE RATHER WELL ON THE ULTIMATE INTENSITY/DEPTH OF THE SYS AS IT LIFTS THROUGH THE REGION. WILL MAINTAIN CONTINUITY AND PREFER A BLEND OF THE 00Z ECMWF AND 00Z GEM. ...UPPER TROUGH DIGGING INTO THE WESTERN U.S. WED THROUGH FRI... PREFERENCE: BLEND OF THE 00Z ECMWF/00Z UKMET AND 00Z ECENS MEAN CONFIDENCE: BELOW AVERAGE ALL OF THE MODELS SHOW A TROUGH DIGGING INTO THE WESTERN U.S. THROUGH THE END OF THE WEEK. THE 12Z NAM IS AN OUTLIER SOLN WITH THE AMOUNT OF ENERGY IT HAS EJECTING OUT ACROSS THE CENTRAL PLAINS BY LATE FRI. THE 00Z ECMWF AND 00Z UKMET ARE THE SLOWEST SOLNS WITH THE LARGER SCALE TROUGH EVOLUTION. THE 00Z GEM AND 12Z GFS SPLIT THE DIFF BETWEEN THE FASTER NAM AND SLOWER ECMWF/UKMET CAMP. THE ENSEMBLE MEANS ARE SPLIT WITH THE ECENS MEAN FAVORING THE ECMWF AND THE GEFS MEAN FAVORING A PROGRESSIVE BUT SOMEWHAT WEAKER VERSION OF THE GFS. CONFIDENCE IS LIMITED BUT WILL FAVOR A BLEND OF THE 00Z ECMWF/00Z UKMET AND 00Z ECENS MEAN WHICH WILL ALLOW FOR MORE ENERGY TO STAY OVER THE FOUR CORNERS REGION THROUGH FRI...AND THIS WILL RESPECT THE LARGER SCALE RIDGE BUILDING JUST OFF THE WEST COAST. ...SURFACE LOW LIFTING NORTHEAST ACROSS THE MIDWEST ON FRI... PREFERENCE: 00Z ECMWF CONFIDENCE: AVERAGE NORTHERN STREAM TROUGHING DIGGING DOWN INTO THE NORTHERN PLAINS BY LATE FRI WILL BE INTERACTING WITH A WEAK SHORTWAVE EJECTING OUT OF THE BASE OF THE DEEPER AND LARGER SCALE TROUGH OVER THE WESTERN U.S. THE RESULT WILL BE A SURFACE LOW THAT LIFTS FROM THE CENTRAL PLAINS NORTHEAST ACROSS THE MIDWEST AND TOWARD THE UPPER GREAT LAKES REGION. THE 00Z UKMET AND 12Z NAM ARE THE SLOWEST SOLNS...WITH THE 00Z GEM AND THE 12Z GFS THE FASTEST. THE 00Z ECMWF SPLITS THE DIFF BETWEEN SLOWER AND FASTER CAMPS AND OFFERS A NICE COMPROMISE SOLN FOR THE TIME BEING. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON