MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 147 PM EST SUN DEC 28 2014 VALID DEC 28/1200 UTC THRU JAN 01/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF ...SHORTWAVE ENERGY SHEARING FROM THE SOUTHERN PLAINS TO THE TN VALLEY/SOUTHEAST... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE SHORTWAVE ENERGY CURRENTLY OVER THE SOUTHERN PLAINS WILL SHEAR EAST OUT OVER THE NEXT COUPLE OF DAYS DOWNSTREAM ACROSS THE TN VALLEY AND SOUTHEAST. A WEAK SURFACE LOW SHOULD CROSS THE INTERIOR SOUTHEAST AND SOUTHERN MID-ATLANTIC LATER TONIGHT AND MON BEFORE GOING OFFSHORE. THERE IS MINIMAL MASS FIELD SPREAD WITH THIS SYS NOW...AND SO A GENERAL MODEL COMPROMISE WILL BE FAVORED. ...PROGRESSIVE SHORTWAVE IMPULSE REACHING THE OH VALLEY/MID-ATLANTIC ON TUES... PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF CONFIDENCE: ABOVE AVERAGE A SHORTWAVE DIGGING ACROSS THE GREAT BASIN CURRENTLY WILL ADVANCE RAPIDLY EAST ACROSS THE CENTRAL PLAINS ON MON...AND THEN EAST ACROSS THE OH VALLEY AND MID-ATLANTIC REGION ON TUES. THE 12Z NAM AND THE 09Z SREF ARE STRONGER OUTLIERS SOLNS AS COMPARED TO THE 12Z GFS AND ALL OF THE NON-NCEP MODELS INCLUDING THE 12Z UKMET/12Z GEM AND 12Z ECMWF. THE PREFERENCE AS SUPPORTED BY THE LATEST GEFS MEAN AND ECENS MEAN IS FOR A FLATTER SHORTWAVE TO MOVE PARTICULARLY ACROSS THE OH VALLEY AND MID-ATLANTIC CONSIDERING THE LARGER SCALE CONFLUENT MID LEVEL FLOW THAT THE ENERGY WILL ENCOUNTER. WILL LEAN TOWARD A BLEND OF THE 12Z GFS AND 12Z ECMWF. ...JET ENERGY/DEEP TROUGH EVOLVING OVER THE WESTERN U.S THROUGH WED... ...CLOSED LOW OVER THE SOUTHWEST BY WED... PREFERENCE: 12Z ECMWF CONFIDENCE: AVERAGE THE MODELS CONTINUE TO ADVERTISE A STRONG UPPER RIDGE DEVELOPING OFFSHORE THE WEST COAST AND NEAR PORTIONS OF THE GULF OF AK. THIS WILL ALLOW A SIGNIFICANT AMOUNT OF SHORTWAVE/JET ENERGY TO DIVE SOUTH DOWN THE EAST SIDE OF THE RIDGE AND INTO THE WESTERN U.S. THROUGH THE PERIOD. THE RESULT WILL GRADUALLY BE A DEEP TROUGH SINKING SOUTH THROUGH THE GREAT BASIN...WITH ULTIMATELY AN ELONGATED CLOSED UPPER LOW DEVELOPING OVER CA/NV THAT WILL BE SETTLING INTO THE SOUTHWEST U.S. BY LATE WED. THE 12Z NAM GRADUALLY BECOMES A SOMEWHAT SLOWER AND DEEPER OUTLIER WITH THE CLOSED LOW EVOLUTION. THE 12Z UKMET IS OVERALL THE FASTEST SOLN AND DRIVES HEIGHT FALLS MORE QUICKLY INTO THE SOUTHWEST BY WED. THE 12Z GFS/12Z ECMWF AND 12Z GEM ARE CLUSTERED IN BETWEEN WITH THE GEM A TAD FASTER AND THE ECMWF A LITTLE SLOWER. THE 12Z GFS FOR ITS PART TAKE MORE ENERGY FARTHER SOUTH THROUGH SOUTHERN CA BY THE END OF PERIOD VS ANY OTHER MODEL. THE 12Z GEFS MEAN KEEPS ITS CLOSED LOW A LITTLE FARTHER NORTH THAN THE DETERMINISTIC GFS. BASED ON THE CURRENT MODEL SPREAD AND CLUSTERING...A SOLN TOWARD THE 12Z ECMWF WILL BE PREFERRED. ...NORTHERN STREAM SHORTWAVE TROUGH DROPPING ACROSS THE UPPER MIDWEST BY TUES... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS INDICATE A NORTHERN STREAM TROUGH DIGGING SOUTH FROM CANADA AND TRAVERSING THE UPPER MIDWEST BY TUESDAY AND THEN ACROSS THE OH VALLEY AND LOWER GREAT LAKES ON WED. THERE IS SUFFICIENTLY STRONG ENOUGH CLUSTERING WITH THE 12Z MODELS THAT A GENERAL MODEL COMPROMISE CAN BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON