MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1219 PM EDT MON APR 14 2014 VALID APR 14/1200 UTC THRU APR 18/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...EASTERN U.S NORTHERN STREAM... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE IS REASONABLY GOOD AGREEMENT ON THE LARGE SCALE WITH THE MODELS SUGGESTING A NEG-TILTING TROUGH ADVANCING ACROSS THE GREAT LAKES AND OH VLY THROUGH TUES...AND THEN CLEARING THE MID-ATLANTIC AND NORTHEAST TUES NIGHT AND EARLY WED. A STRONG FRONTAL ZONE WILL CROSS THE REGION...AND THE MODELS INDICATE A WELL-DEFINED WAVE OF LOW PRESSURE DEVELOPING ALONG THE FRONT OVER THE OH VLY TONIGHT WHICH WILL THEN ADVANCE NNEWD ACROSS THE LWR GRT LAKES REGION AND ST LAWRENCE RIVER VLY ON TUES. THE LATEST MODELS ARE IN SUFFICIENT AGREEMENT THAT A GENERAL MODEL COMPROMISE SHOULD SUFFICE TO ADDRESS IN LINGERING SMALL SCALE DIFFS IN THE GUIDANCE. ...EASTERN U.S SOUTHERN STREAM... PREFERENCE: NON-GEM CONSENSUS CONFIDENCE: ABOVE AVERAGE A VIGOROUS SHORTWAVE TROUGH EXITING OUT INTO THE CNTRL PLAINS ATTM WILL FOLLOW IN BEHIND THE INITIAL LARGE SCALE SFC COLD FRONT APPROACHING THE EASTERN U.S. TODAY AND TUES. THIS ENERGY WILL DIVE INTO THE GULF COAST STATES BEFORE LIFTING ALONG THE EASTERN SEABOARD. THE LATEST GUIDANCE SUPPORTS THE IDEA OF THIS ENERGY DEVELOPING A WEAK WAVE OF LOW PRESSURE OVER ERN NC LATE TUES BEFORE THE FRONT THEN MOVES OFFSHORE. THE 00Z GEM IS SOMEWHAT OF A SLOWER/DEEPER OUTLIER COMPARED TO THE MULTI-MODEL CONSENSUS...AND THUS WILL PREFER A NON-GEM CONSENSUS SOLN ATTM. ...TROUGH DIPPING DOWN FROM THE CANADIAN PRAIRIES BY MIDWEEK... PREFERENCE: 12Z GFS/00Z ECMWF COMPROMISE CONFIDENCE: AVERAGE THERE CONTINUES TO BE A FAIR AMT OF MODEL SPREAD WITH THE DEPTH AND ESP THE TIMING OF THIS NRN STREAM TROUGH THAT DIGS SOUTH FROM CNTRL CANADA AND TWD THE NRN PLAINS WED AND THURS. THE 12Z NAM IS A BIT OF A WEAK/FAST OUTLIER EARLY IN THE PERIOD...BUT THEN BY THE TIME THE ENERGY MAKES IT SOUTH INTO THE NRN PLAINS ON THURS...IT SUGGESTS A FAIRLY ROBUST MID LVL CLOSED LOW. THE 12Z GFS/00Z GEM AND ESP THE 00Z ECMWF ARE SLOWER TO SINK THE ENERGY SOUTH AND ARE MORE ELONGATED W/E WITH THE LARGER SCALE TROUGH. THE 00Z UKMET IS SLOWER TOO...SUGGESTS A SOMEWHAT BETTER DEFINED CLOSED LOW BY THURS OVER SRN CANADA. THE LATEST GEFS MEAN AND ECENS MEAN SUPPORT THE SLOWER/ELONGATED ORIENTATION OF THE HEIGHT FALLS. MUCH OF THE EVOLUTION OF THIS IS DEPENDENT ON HOW THE LARGER SCALE MEAN RIDGE NEAR ALASKA AND NWRN CANADA EVOLVES. WILL DISMISS THE 12Z NAM AS AN OUTLIER SOLN...WITH THE REMAINING MODELS AT LEAST MORE STRONGLY CLUSTERED. THE 00Z ECMWF AND 12Z GFS TEND TO HAVE STRONGER SUPPORT BASED ALONE ON ENSEMBLE SUPPORT...AND SO WILL PREFER A BLEND OF THE GFS AND ECMWF ATTM. ...PACIFIC SHORTWAVE TROUGH DIGGING TOWARD THE CENTRAL ROCKIES/PLAINS/UPPER MIDWEST... ...LOW PRESSURE EVOLUTION OVER THE NORTHERN PLAINS/UPPER MIDWEST/UPPER GREAT LAKES... PREFERENCE: 12Z GFS/00Z ECMWF COMPROMISE CONFIDENCE: AVERAGE A PORTION OF THE SHORTWAVE TROUGH CURRENTLY APPROACHING THE PACIFIC NORTHWEST WILL ADVANCE SEWD AND DIG TOWARD THE CNTRL ROCKIES BY WED...BEFORE THEN PROGRESSIVELY EJECTING EAST ACROSS THE PLAINS AND LIFTING NEWD TWD THE UPR MIDWEST BY EARLY THURS. ALL THE WHILE...LOW PRESSURE WILL BE REDEVELOPING IN THE LEE OF THE NRN ROCKIES AND MOVING INITIALLY SEWD AND THEN NEWD UP ACROSS THE PLAINS AND TWD THE UPR MIDWEST/UPR GRT LAKES REGION BY THURS. ALOFT...THE 12Z GFS AND 00Z ECMWF ARE A LITTLE FASTER THAN THE MULTI-MODEL CONSENSUS...WITH THE 12Z NAM THE SLOWEST AND THE DEEPEST. AT THE SFC...THE 12Z NAM IS THE STRONGEST SOLN...FOLLOWED BY THE 12Z GFS/00Z ECMWF WHICH CLUSTER VERY WELL...AND THEN THE 00Z GEM AND 00Z UKMET WHICH ARE FLATTER/WEAKER AND ESP BY LATE WED/EARLY THURS ACROSS THE UPR GRT LAKES REGION. BASED ON STRONGER MODEL CLUSTERING AND THE TREND OF THE GFS TOWARD THE ECMWF SOLN...WILL PREFER A GFS/ECMWF COMPROMISE. ...SHORTWAVE ENERGY ATTEMPTING TO AMPLIFY OVER THE CENTRAL/SOUTHERN ROCKIES/SOUTHERN PLAINS... ...LOW PRESSURE DEVELOPING OVER THE SOUTHERN HIGH PLAINS BY THURSDAY... PREFERENCE: 12Z GFS/00Z ECMWF COMPROMISE CONFIDENCE: AVERAGE PACIFIC SHORTWAVE ENERGY DIGGING SEWD ACROSS THE CNTRL/SRN ROCKIES BY WED WILL BE EJECTING OUT INTO THE SRN PLAINS ON THURS AND WILL BE ATTEMPTING TO DEVELOP SFC LOW PRESSURE ALONG THE SRN END OF A FRONTAL ZONE DRAPED SWWD FROM THE MIDWEST DOWN TO THE SRN HIGH PLAINS. THE 12Z NAM IS A RELATIVELY STRONG OUTLIER ALOFT...BUT IS NOT TOO DIFFERENT FROM THE GLOBAL MODEL CONSENSUS. THE 12Z GFS AND 00Z ECMWF CLUSTER THE BEST SFC AND ALOFT...AND HAVE REASONABLY GOOD SUPPORT FROM THE 00Z GEM AND 00Z UKMET. THUS WILL PREFER A GFS/ECMWF COMPROMISE. ...NEXT SHORTWAVE APPROACHING THE PACIFIC NORTHWEST BY THURSDAY... PREFERENCE: NON-GFS CONSENSUS CONFIDENCE: AVERAGE THERE WILL BE ANOTHER SHORTWAVE TROUGH ARRIVING ACROSS THE PAC NORTHWEST BY THURS. THE 12Z GFS AND TO AN EXTENT THE 00Z UKMET ARE FAST OUTLIERS WITH THIS SYS. THE 12Z NAM IS A TAD SLOWER...WITH THE 00Z GEM AND 00Z ECMWF THE SLOWEST. THE LATEST GEFS MEAN IS SLOWER THAN THE GFS BUT A LITTLE FASTER THAN THE ECMWF. THE LATEST ECENS MEAN IS ACTUALLY EVEN A LITTLE SLOWER THAN THE ECMWF/GEM CAMP. DESPITE THE PROGRESSIVE LARGER SCALE FLOW PATTERN ACROSS THE CNTRL/ERN PAC AND AIMED INTO THE NORTHWEST...THE GFS IS LIKELY A LITTLE TOO FAST. SO WILL PREFER A NON-GFS CONSENSUS ATTM. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON