MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1143 PM EST WED MAR 04 2015 VALID MAR 05/0000 UTC THRU MAR 08/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...STRONG HEIGHT FALLS MOVING FROM THE CENTRAL U.S. TOWARD THE NORTHEASTERN STATES... ...WAVY FRONTAL ZONE EXITING THE EASTERN SEABOARD... PRELIMINARY PREFERENCE: A NON-12Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE WATER VAPOR IMAGERY TONIGHT SHOWED A BROAD POSITIVELY-TILTED TROF MOVING FROM THE CENTRAL U.S. TOWARD THE MS RIVER VALLEY. IN ADVANCE OF THIS FEATURE...THE 500-MB HEIGHT ANALYSIS AND BLENDED-TPW GRAPHIC SHOWED STRONG MID-LEVEL CONFLUENCE DOWNSTREAM COLLOCATED WITH AN AREA OF ENHANCED GULF INFLOW. THIS PATTERN HAS BEEN RESPONSIBLE FOR AN EXPANSIVE AREA OF MIXED PRECIPITATION FROM THE SOUTHERN PLAINS UP TO THE MID-ATLANTIC. OVERALL...THE MODELS HAVE COME INTO DECENT AGREEMENT REGARDING THE PASSAGE OF THE MID-LEVEL TROF. THERE IS A LITTLE MORE UNCERTAINTY WITH THE STRENGTH AND LOCATION OF THE COLD FRONT WHICH SAGS SOUTHWARD TOWARD THE SOUTHEASTERN U.S. BY LATE THURSDAY. THE 12Z CMC IS THE ONE OF THE STRONGER SOLUTIONS ATTEMPTING TO DEVELOP A MORE PRONOUNCED AREA OF LOW PRESSURE OFFSHORE OF GA. WILL STEER AWAY FROM THIS IDEA AND FAVOR A NON-12Z CMC MODEL COMPROMISE. ...SECONDARY SHORTWAVE CROSSING THE MIDDLE MS VALLEY BY LATE THURSDAY... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET FORECAST CONFIDENCE: AVERAGE IN THE WAKE OF THE PRONOUNCED UPPER TROF EXITING THE EASTERN SEABOARD WILL BE A LOWER AMPLITUDE SYSTEM CROSSING THE MIDDLE MS VALLEY BY 06/06Z. GENERAL AGREEMENT IS NOTED WITH THE EXCEPTION OF THE 12Z CMC WHICH IS FARTHER SOUTH WITH THE POSITION OF THE SHORTWAVE. BY LATE FRIDAY EVENING...THE 00Z NAM/GFS BEGIN TO MIGRATE AHEAD OF THE OTHER SOLUTIONS WHICH BRINGS THE REINFORCING SHOT OF COLD AIR IN MORE QUICKLY. PLAN ON LEANING ON THE CONSENSUS OF THE OTHER CLUSTERED SOLUTIONS FEATURING THE 12Z ECMWF/UKMET. ...ADDITIONAL SHORTWAVES REACHING THE NORTHERN TIER THIS WEEKEND... ...WEAK SURFACE LOW MOVING ACROSS THE GREAT LAKES... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF ENSEMBLE/21Z SREF MEANS FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE BROAD UPPER CYCLONIC FLOW WILL CONTINUE THROUGHOUT THE PERIOD AS ADDITIONAL SHORTWAVES MOVE FROM CENTRAL CANADA TOWARD THE NORTHERN TIER OF THE U.S. THERE ARE QUITE A FEW TIMING DIFFERENCES IN NOTED IN THE MODEL SOLUTIONS. ON THE SLOWER SIDE OF THE EQUATION ARE THE 00Z NAM/GFS AND 18Z GEFS MEAN WHILE THE REMAINING MODELS SUGGEST A FASTER SOLUTION. THE GUIDANCE DOES SEEM TO BE STRUGGLING WITH THE STRENGTH OF THE APPROACHING SHORTWAVES ALONG WITH THE TIMING. THE 12Z ECMWF SUITE IS EMPHATIC ABOUT A DEEPER SURFACE SOLUTION RELATIVE TO SOME OF THE OTHER FLATTER SOLUTIONS. GIVEN THE INHERENT SPREAD...WILL FAVOR A COMBINATION OF ENSEMBLE MEANS UNTIL THE DETERMINISTIC MODELS SHOW A BIT MORE CONSISTENCY. WPC RECOMMENDS A COMBINATION OF THE 12Z ECMWF ENSEMBLE/21Z SREF MEANS. ...SLOW MOVING CLOSED LOW IN THE VICINITY OF NORTHERN BAJA CA... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/CMC FORECAST CONFIDENCE: AVERAGE SOME FORM OF A REX BLOCK IS NOTED IN THE GUIDANCE ACROSS THE WESTERN U.S. AS THE PERSISTENT UPPER RIDGE REMAINS IN PLACE ACROSS THIS SIDE OF THE COUNTRY. BOUNDED TO ITS SOUTH WILL BE A COMPACT CLOSED LOW WHICH IS FORECAST TO SLIDE EASTWARD ACROSS NORTHERN BAJA CA BY MIDDAY FRIDAY. THE GUIDANCE VARY WITH HOW QUICKLY TO EJECT THIS SYSTEM TOWARD THE SOUTHERN HIGH PLAINS. AT THIS TIME...THE 00Z NAM/GFS ARE THE FASTER SIDE OF THE SPREAD WHICH IS NOT SUPPORTED GIVEN WOULD RATHER STAY ON THE SLOWER SIDE WITH A CLOSED LOW IN THE FORECAST. THE PLAN IS TO STAY AT THE CENTER OF THE SOLUTION SPREAD BOUNDING THE QUICKER 00Z NAM/GFS AND THE SLOWER 12Z UKMET. THE RECOMMENDATION IS A BLEND OF THE 12Z ECMWF/CMC AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER