MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 156 AM EST MON JAN 27 2014 VALID JAN 27/0000 UTC THRU JAN 30/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS NO SIGNIFICANT INITIALIZATION ERRORS WERE SEEN IMPACTING THE SHORT RANGE FORECAST. ...ARCTIC OUTBREAK LED BY LOW PRESSURE CROSSING OVER THE GREAT LAKES... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS HAVE COME INTO RATHER STRONG AGREEMENT WITH THE DETAILS OF THE SFC LOW PASSAGE ACROSS THE GREAT LAKES REGION AND THROUGH THE ST LAWRENCE RIVER VLY ON MON. ADDITIONALLY...THE MODELS ARE SHOWING REASONABLY GOOD AGREEMENT WITH THE TIMING OF THE ARCTIC FRONTAL PASSAGE ACROSS THE EASTERN HALF OF THE NATION. SO...WILL PREFER A GENERAL MODEL COMPROMISE TO RESOLVE ANY LINGERING SMALL SCALE DIFFERENCES. ...SOUTHERN STREAM TROUGH/CLOSED LOW CROSSING SOUTHERN CALIFORNIA AND DROPPING DOWN OVER THE BAJA PENINSULA/MEXICO MON AND TUES... PREFERENCE: BLEND OF THE 00Z ECMWF/00Z UKMET CONFIDENCE: BELOW AVERAGE THE 00Z NAM AND 00Z GFS HAVE TRENDED SLOWER RESPECT TO THE CLOSED LOW THAT IS FORECAST TO REACH BAJA/MEXICO ON TUES. THEREAFTER...THE 00Z NAM AND 00Z GFS INDICATE A PROGRESSIVE/SHEARED SOLN WITH THE CLOSED LOW WEAKENING INTO AN OPEN TROUGH AXIS AND PROPAGATING ACROSS NRN MEXICO BEFORE SHEARING OUT ACROSS THE GULF COAST STATES. THE NON-NCEP SOLNS...INCLUDING THE 00Z ECMWF/00Z UKMET AND 00Z GEM GLOBAL HAVE ALL TRENDED A BIT MORE PROGRESSIVE AND BEGIN TO OPEN THE CLOSED LOW UP OVER CNTRL MEXICO BY EARLY WED. THE LATEST MODELS ARE AT LEAST BEGINNING TO CONVERGE TOWARD A MIDDLE OF THE ROAD CONSENSUS AS COMPARED TO PREV MODEL CYCLES. AS IT STANDS RIGHT NOW....THE 00Z GEM GLOBAL IS THE SLOWEST SOLN WITH THE ENERGY...COMPARED TO THE 00Z NAM/00Z GFS CAMP WHICH IS THE FASTEST. THE 00Z ECMWF AND 00Z UKMET SPLIT THE DIFF AND CLUSTER VERY WELL. THE LATEST GEFS MEAN IS CLOSE TO THE SOLN IF THE DETERMINISTIC GFS...WITH THE LATEST ECENS MEAN SLOWER AND ACTUALLY CLOSE TO THE 00Z GEM GLOBAL SOLN. BASED ON THE LATEST MODEL TRENDS AND CLUSTERING...WILL FAVOR THE 00Z ECMWF AND 00Z UKMET SOLNS SINCE THEY AT LEAST DO NOT REPRESENT OUTLIER CAMPS WITH THE 00Z MODEL CYCLE. CONFIDENCE THOUGH REMAINS LIMITED. ...BROAD SHORTWAVE DIGGING INTO THE SOUTHERN PLAINS/LOWER MS VALLEY... ...POTENTIAL WINTER STORM FOR THE GULF COAST/SOUTHEAST... PREFERENCE: BLEND OF THE 00Z ECMWF/00Z UKMET CONFIDENCE: BELOW AVERAGE THE MODELS CONTINUE TO ADVERTISE A BROAD SHORTWAVE TROUGH AMPLIFYING SOMEWHAT AS IT DROPS SOUTHEAST ACROSS THE CNTRL/SRN PLAINS AND THE MS/OH/TN VLYS TUES AND WED. THE 00Z MODEL CYCLE SHOWS SOME LESSENING OF THE OVERALL MODEL MASS FIELD SPREAD AND THE RELATED QPF SPREAD...BUT THERE REMAINS LOCALLY VERY SIGNIFICANT DIFFERENCES WHICH MAKE THE DIFFERENCE BETWEEN A MODEST VS VERY SIGNIFICANT WINTER STORM FOR PORTIONS OF THE GULF COAST STATES AND SOUTHEAST. THE 00Z NAM AND 00Z GFS BOTH CONTINUE TO BE SLOWER AND MORE AMPLIFIED WITH THE AFOREMENTIONED SHORTWAVE ENERGY...WHICH DRIVES A MUCH WETTER SOLN ACROSS THE GULF COAST STATES AND THE SOUTHEAST COASTAL PLAIN. BOTH OF THESE MODELS ARE ALSO IN PART MORE ENERGETIC BECAUSE OF THEIR ATTEMPT TO INCORPORATE MORE SRN STREAM ENERGY AND MOISTURE OUT OF NRN MEXICO RELATING TO THE CLOSED LOW EVOLUTION OVER THE BAJA PENINSULA. THE NON-NCEP SOLNS...INCLUDING THE 00Z ECMWF/00Z UKMET AND THE 00Z GEM GLOBAL ALL SUPPORT A LESS-AMPLIFIED AND MORE PROGRESSIVE NRN STREAM SHORTWAVE CROSSING THE MS/OH/TN VLYS TUES AND WED. THE NON-NCEP SOLNS WHILE THEY HAVE TRENDED WETTER...ARE STILL DRIER THAN THE NCEP SOLNS. CONSIDERING THE DEGREE OF BROADLY CONFLUENT FLOW ALOFT THAT THIS SHORTWAVE ENERGY WILL BE ENCOUNTERING ACROSS THE EAST...A MORE AMPLIFIED NAM/GFS SOLN DOES NOT SEEM PARTICULARLY REALISTIC. THIS WOULD SUGGEST LESS BACKING OF THE MID LEVEL FLOW ALONG THE EAST COAST. THIS COUPLED WITH CONCERNS ABOUT THE NAM AND GFS HANDLING OF ENERGY CROSSING NRN MEXICO SUGGESTS STILL LEANING AWAY FROM THE NCEP SOLNS...AND SUPPORTS THE IDEA OF A VERY TIGHT/CONCENTRATED PCPN GRADIENT ACROSS THE GULF COAST STATES AND SOUTHEAST COASTAL PLAIN. WILL AGAIN FAVOR A BLEND OF THE ECMWF/UKMET SOLNS. CONFIDENCE CONTINUES TO REMAIN LIMITED. ...PACIFIC NORTHWEST... PREFERENCE: BLEND OF THE 00Z GFS/00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE PERSIST STRONG MEAN LAYER RIDGE ALONG THE WEST COAST WILL BE BREAKING DOWN BY TUES NIGHT AND WED AS SHORTWAVE TROUGHING ADVANCES EASTWARD TOWARD THE WEST COAST AND PAC NORTHWEST. THE 00Z NAM AND 00Z UKMET ARE A BIT SLOWER THAN THE MULTI-MODEL CONSENSUS WITH THE ENERGY. THE 00Z GFS/00Z ECMWF AND 00Z GEM GLOBAL ALL CLUSTER MORE STRONGLY AND HAVE STRONGER ENSEMBLE SUPPORT FROM THE LATEST GEFS MEAN AND ECENS MEAN. WILL FAVOR A BLEND OF THE 00Z GFS AND 00Z ECMWF AS A RESULT. ...CLOSED LOW REACHING SOUTHERN CANADA LATE WED... PREFERENCE: BLEND OF THE 00Z GFS/00Z ECMWF CONFIDENCE: AVERAGE THE MODELS SHOW GOOD AGREEMENT ON ANOTHER NRN STREAM CLOSED LOW DROPPING SOUTH ACROSS SRN CANADA BY WED AND ENCROACHING ON THE UPR MIDWEST BY EARLY THURS. THE 00Z NAM IS THE FASTEST TO PIVOT THE HEIGHT FALLS ACROSS THE REGION...WITH THE 00Z UKMET AND 00Z GEM GLOBAL THE SLOWEST. THE 00Z GFS AND 00Z ECMWF CLUSTER TOGETHER RATHER WELL IN THE MIDDLE. THE LATEST GEFS MEAN AND ECENS MEAN SUPPORT THE GFS/ECMWF CAMP AND SO THIS WILL BE THE PREFERENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON