MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1255 PM EDT FRI MAR 21 2014 VALID MAR 21/1200 UTC THRU MAR 25/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE TROUGH/SURFACE LOW ADVANCING FROM THE MIDWEST TO THE NORTHEAST THROUGH SAT... PREFERENCE: BLEND OF THE 00Z ECMWF/00Z UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE A STRONG SHORTWAVE CROSSING THE UPPER MIDWEST THIS MORNING IS EXPECTED TO CONTINUE ITS PROGRESSION EASTWARD REACHING INTERIOR NEW ENGLAND SAT AFTERNOON. A SURFACE LOW ALL THE WHILE WILL BE ADVANCING ACROSS THE LWR GRT LAKES REGION AND NEW ENGLAND. THE STRONGER MODEL CLUSTERING WITH THE SFC LOW TRACK CONSISTS OF THE 00Z ECMWF AND 00Z UKMET. THE 00Z GEM GLOBAL IS A TAD SLOWER THAN THE GLOBAL MODEL CONSENSUS. THE 12Z NAM IS CLOSE TO THE ECMWF/UKMET CAMP...BUT THE 12Z GFS A TAD NORTH AND A LITTLE STRONGER THAN THE MULTI-MODEL CONSENSUS. WILL FAVOR A BLEND OF THE 00Z ECMWF AND 00Z UKMET ATTM. ...SHORTWAVE TROUGH CROSSING THE NORTHERN PLAINS/MIDWEST/OHIO VALLEY/GREAT LAKES SAT AND SUN... ...SURFACE LOW DEVELOPMENT OFFSHORE THE SOUTHEAST ON SUN AND MON... PREFERENCE: 00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE A NEW NRN STREAM SHORTWAVE TROUGH WILL BE ELONGATED AND POSITIVELY TILTED ON SAT AS IT DROPS SOUTH INTO THE NRN PLAINS AND THE UPR MIDWEST. THE ENERGY WILL DROP ACROSS THE OHIO VALLEY AND GRT LAKES THROUGH SUN...AND WILL BE INTERACTING WITH A BAROCLINIC ZONE THAT WILL HAVE SETTLED INTO THE SOUTHEAST. OVERALL...THERE IS PRETTY GOOD MASS FIELD AGREEMENT WITH THE MODELS ALOFT...ALTHOUGH THE NAM AND UKMET APPEAR A LITTLE TOO STRONG WITH THE SHORTWAVE TROUGH BY SUN. THE NAM IS ALSO A BIT SLOWER. THE GFS APPEARS TO BE THE WEAKEST/FLATTEST WITH THE SYS WITH THE ECMWF AND GEM GLOBAL SPLITTING THE DIFF. AT THE SFC...THE NAM IS A LITTLE SLOWER WITH THE EXITING LOW CENTER THAT DEVELOPS AND EXITS OFFSHORE THE SOUTHEAST ON SUN. THE UKMET BECOMES A DEEPER OUTLIER. THE GFS IS THE WEAKEST/FASTEST WITH THE LOW CENTER...WITH THE ECMWF AND GEM GLOBAL SPLITTING THE DIFF BETWEEN STRONGER AND WEAKER CAMPS. WILL PREFER A SOLN TWD THE 00Z ECMWF WHICH HAS VERY STRONG AGREEMENT FROM THE ECENS MEAN. ...SHORTWAVE ENERGY DIGGING SOUTHEAST THROUGH THE NORTHERN ROCKIES/GREAT PLAINS BY EARLY NEXT WEEK... PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF CONFIDENCE: AVERAGE A HIGHLY AMPLIFIED LARGE SCALE MID-LATITUDE FLOW PATTERN WILL BE SETUP OVER WRN NORTH AMERICA EARLY NEXT WEEK WITH A RIDGE BUILDING ACROSS THE WRN CONUS WITH LARGE SCALE TROUGH DOWNWIND OVER THE MIDWEST. ON MON AND TUES...THE MODELS INDICATE MULTIPLE NRN STREAM SHORTWAVE IMPULSES SLIDING SOUTHEASTWARD THROUGH THE NRN/CNTRL ROCKIES AND OUT INTO THE PLAINS/MIDWEST. ONE PIECE OF ENERGY EXITING THE NRN/CNTRL ROCKIES ON MON ADVANCES ACROSS THE MID MS VLY BY TUES. THE 12Z NAM IS THE FASTEST WITH THIS ENERGY...WITH THE 00Z UKMET THE SLOWEST. THE 12Z GFS/00Z ECMWF AND 00Z GEM GLOBAL SPLIT THE DIFF. REGARDING THE SECOND IMPULSE WHICH ARRIVES ACROSS SRN CANADA AND THE NRN PLAINS ON TUES...THE 12Z NAM AND 00Z UKMET WERE THE SLOWER SOLNS...WITH THE 12Z GFS/00Z ECMWF AND 00Z GEM GLOBAL FASTER. OVERALL...THE MODELS ARE NOT SIGNIFICANTLY DIFF WITH THEIR MASS FIELD DETAILS ON THE LARGER SCALE...BUT THE STRONGER MODEL CLUSTERING WITH BOTH SHORTWAVE IMPULSES FAVORS A GFS/ECMWF BLEND. ...SOUTHERN STREAM TROUGH POTENTIALLY CUTTING OFF OVER SOUTHERN CALIFORNIA BY LATE IN THE PERIOD... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE AS AN UPR RIDGE BUILDS ACROSS THE WESTERN U.S...MODELS DEPICT ENERGY PINCHING OFF UNDERNEATH IN THE VICINITY OF SRN CA BY LATE SUN AND MON. ALL OF THE MODELS SHOW THIS SCENARIO...AND WHILE THERE ARE SOME MINOR SMALL SCALE DIFFS RELATING TO DEPTH OF THE TROUGHING AND POSSIBLE CLOSING OFF OF A MID LVL LOW CENTER...THE MODELS AGREE ON THE LARGER SCALE EVOLUTION OF THIS SYS. THEREFORE...WILL PREFER A GENERAL MODEL COMPROMISE. www.wpc.ncep.noaa.gov/html/model2.shtml... ORRISON