MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 231 AM EDT WED MAY 03 2017 VALID MAY 03/0000 UTC THRU MAY 06/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING FINAL MODEL PREFERENCES/CONFIDENCE ...SHORTWAVE CROSSING THE NORTHEAST ON WED... PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE A SHORTWAVE OVER THE GREAT LAKES REGION WILL CROSS THE NORTHEAST ON WED BEFORE THEN CROSSING THE CANADIAN MARITIMES WED NIGHT/THURS.THE MODES ARE IN GOOD MASS FIELD AGREEMENT WITH THIS ENERGY...SO A GENERAL MODEL BLEND WILL BE PREFERRED. ...DIGGING SHORTWAVE CROSSING THE CENTRAL/SOUTHERN PLAINS THROUGH WED... ...DEEP CLOSED LOW DEVELOPMENT OVER THE LOWER MS/TN VALLEY THURS... ...MOVING INTO THE EASTERN U.S. BY FRI WHILE GOING NEGATIVE TILT... ...PHASING NORTHERN STREAM ENERGY... PREFERENCE: BLEND OF THE 00Z GFS/00Z UKMET AND 00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE A SHORTWAVE AMPLIFYING ACROSS THE CENTRAL/SOUTHERN PLAINS REGION THROUGH WED WILL EJECT EAST WITH A STRONG CLOSED MID LEVEL DEVELOPING AND CROSSING THE LOWER MS/TN VALLEY REGION THROUGH THURS. ALL OF THIS ENERGY ALONG WITH A ROBUST SURFACE LOW WILL EJECT UP ACROSS THE OH VALLEY THROUGH FRI AND THEN INTO THE LOWER GREAT LAKES REGION SAT WHERE MODELS SHOW A SIGNIFICANT AMOUNT OF PHASING OCCURRING WITH NORTHERN STREAM SHORTWAVE ENERGY DROPPING SOUTHEAST FROM ONTARIO. THIS WILL ALONG FOR AN ELONGATING AND NEGATIVELY TILTED LONGWAVE TROUGH MOVING INTO THE EASTERN U.S. WITH A STRONG CLOSED LOW THAT EVENTUALLY ENDS UP OVER THE LOWER GREAT LAKES. THE 00Z NAM GRADUALLY TEND TO BE A LITTLE WEAKER THAN MOST OF THE GLOBAL MODELS WITH ITS TROUGH/CLOSED LOW EVOLUTION AND ALSO ITS SURFACE LOW. THE NAM ALSO IS A LITTLE TOO SLOW IT APPEARS WITH ITS COLD FRONT CROSSING THE GULF COAST STATES AND SOUTHEAST. THE 00Z CMC TENDS TO HAVE THE SAME CONCERN AS THE NAM WITH A MODESTLY WEAKER EVOLUTION. THE 00Z GFS/00Z UKMET AND 00Z ECMWF ALL SHOW BETTER CLUSTERING TOWARD A SOMEWHAT STRONGER EVOLUTION THAT HAS REASONABLY GOOD ENSEMBLE SUPPORT AS WELL. THE UKMET WHICH WAS LIKELY TUCKING ITS SURFACE LOW TOO FAR BACK TO THE WEST BY SAT OVER THE LOWER GREAT LAKES HAS SHIFTED IT A BIT FARTHER EAST AND IN GOOD AGREEMENT WITH THE GFS/ECMWF CLUSTER. A BLEND OF THE GFS/UKMET AND ECMWF WILL SUFFICE AT THIS TIME. ...LONGWAVE TROUGH APPROACHING THE WEST COAST BY FRI... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE ALL OF THE MODELS SUGGEST A DEEP UPPER TROUGH APPROACHING THE WEST COAST BY FRI AND THEN EDGING INLAND ON SAT AS THE OVERALL LARGE SCALE PATTERN REMAINS HIGHLY AMPLIFIED. IN FACT...A RATHER CLASSIC LOOKING OMEGA BLOCK IS ADVERTISED BY THE GUIDANCE BY THE END OF THE PERIOD OVER THE CONUS. THE 00Z NAM SUGGESTS SOMEWHAT MORE PROGRESSIVE HEIGHT FALLS OVER THE PACIFIC NORTHWEST COMPARED TO ALL OF THE GLOBAL MODELS AND WILL BE DISMISSED. THE BETTER CLUSTERING OF SOLUTIONS LIES WITH THE GLOBAL MODELS LED BY THE 00Z GFS AND 00Z ECMWF OVERALL. SO A GFS/ECMWF BLEND WILL BE PREFERRED. WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/ WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/ ORRISON