MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1258 AM EDT WED MAY 24 2017 VALID MAY 24/0000 UTC THRU MAY 27/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...CLOSED UPPER LOW OVER THE UPPER MIDWEST DIGGING ACROSS THE MIDDLE/LOWER MS VALLEY LATE WED...MOVING TO THE EAST COAST THU...EXITING NEW ENGLAND FRI... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 0Z GFS/NAM AND 12Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE OVERALL MODELS ARE IN PRETTY GOOD AGREEMENT WITH THE EVOLUTION OF THIS SYSTEM AS IT PUSHES ACROSS THE EASTERN PORTION OF THE COUNTRY. THE 12Z GEM APPEARS A BIT DEEPER THAN THE CONSENSUS WITH THE SURFACE AND MID LEVEL LOW OVER THE MID ATLANTIC BY 0Z FRIDAY AND APPEARS TO REPRESENT A LESS LIKELY OUTCOME. ALSO NOTE THAT THE 12Z UKMET BECOMES A BIT STRONGER WITH THE MID LEVEL LOW BY 12Z FRIDAY...RESULTING IN A SLIGHTLY SLOWER NORTHEASTWARD PROGRESSION OF THE SYSTEM. FOR NOW PREFER TO STICK CLOSER TO A BLEND OF THE 0Z GFS/NAM AND 12Z ECMWF...WHICH ALL SEEM TO REPRESENT PLAUSIBLE SOLUTIONS AND ARE GENERALLY PRETTY CLOSE TO EACH OTHER. ...UPPER TROUGH MOVING ACROSS THE NORTHWEST THROUGH MID WEEK... ...DEVELOPING LONGWAVE TROUGH OVER THE WEST... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: AVERAGE A CLOSED DEEP LAYER LOW WILL MOVE ACROSS ALBERTA TODAY AND INTO SASKATCHEWAN THURSDAY...WITH THIS SYSTEM HELPING TO CARVE OUT A LONGWAVE TROUGH OVER OVER THE WEST THROUGH THE WEEK. THIS PROCESS WILL BE AIDED BY SHORTWAVE ENERGY DIVING SOUTHEAST ALONG THE PERIPHERY OF THE CLOSED LOW INTO THE PACIFIC NORTHWEST AND INTERMOUNTAIN WEST INTO FRIDAY. THIS ENERGY WILL EJECT EASTWARD TOWARDS THE WESTERN PLAINS BY EARLY SATURDAY...WITH SURFACE LOW DEVELOPMENT POSSIBLE OVER THE SOUTHERN/CENTRAL PLAINS BY 12Z SATURDAY. MODELS ARE GENERALLY IN PRETTY CLOSE AGREEMENT WITH THE CLOSED LOW AS IT MOVES ACROSS SOUTHERN CANADA...HOWEVER BEGIN TO SEE SOME DIFFERENCES DEVELOP AS EARLY AS 12Z THURSDAY WITH THE SHORTWAVE ENERGY DROPPING SOUTH INTO THE PACIFIC NORTHWEST. THESE DIFFERENCES PERSIST...SO THAT BY 12Z SATURDAY THE LOCATION AND DEPTH OF THE TROUGH AXIS OVER THE INTERMOUNTAIN WEST/ROCKIES DIFFERS BETWEEN MODEL SOLUTIONS...WHICH IN TURN IMPACTS THE LATITUDE AND STRENGTH OF THE DEVELOPING PLAINS SURFACE LOW. THE 0Z GFS ENDS UP A BIT QUICKER AND STRONGER WITH THE ENERGY AS IT MOVES INTO WY/CO BY 0Z SAT...WITH THE 12Z ECMWF SLOWER AND MORE STRUNG OUT. THUS THE MID LEVEL FLOW ENDS UP A BIT MORE AMPLIFIED IN THE GFS COMPARED TO THE ECMWF. NOTHING REALLY STANDS OUT IN MODEL TRENDS OR THE ENSEMBLE DATA TO PREFER ONE SOLUTION OVER ANOTHER AT THIS POINT. THE NAM/UKMET/GEFS ARE CLOSER TO THE GFS SOLUTION AND THE GEM/EC MEAN CLOSER TO THE ECMWF. THUS FOR NOW WOULD PREFER TO JUST GO DOWN THE MIDDLE AND STAY PRETTY CLOSE TO A GENERAL MODEL BLEND THROUGH 12Z SATURDAY. ...SUBTLE SHORTWAVE ENERGY AND POSSIBLE SURFACE LOW MOVING EAST FROM THE MS VALLEY INTO THE OH VALLEY FRIDAY INTO SATURDAY... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF/UKMET BLEND CONFIDENCE: AVERAGE MODELS ALL SHOW SOME WEAK SHORTWAVE ENERGY MOVING EAST IN ZONAL FLOW ACROSS THE OH VALLEY SOMETIME FRIDAY INTO SATURDAY...WITH A POSSIBLE SURFACE LOW REFLECTION AS WELL. THE 0Z NAM APPEARS TO BE SUFFERING FROM SOME CONVECTIVE FEEDBACK ISSUES RESULTING IN A FURTHER NORTH LOW BY 0Z SATURDAY. THE 12Z GEM ALSO APPEARS TOO FAR NORTH. THE GFS HAS CONSISTENTLY BEEN QUICKER AND GENERALLY WEAKER THAN THE OTHER GUIDANCE WITH THIS FEATURE. THIS MAY IN PART BE DUE TO A SLIGHTLY STRONGER SHORTWAVE MOVING ACROSS THE DAKOTAS AT 0Z FRI HELPING KICK THE SOUTEHRN WAVE EAST QUICKER. WHILE NOT IMPOSSIBLE...WILL LEAN AGAINST THIS FOR NOW SINCE ALL THE OTHER DETERMINISTIC GUIDANCE ARE AGAINST IT. THE ECMWF/UKMET ARE THE TWO PIECES OF GUIDANCE THAT APPEAR TO FIT MORE IN THE CENTER OF THE MODEL SPREAD WITH REGARDS TO BOTH THE TIMING AND LATITUDE OF THE WAVE/LOW. WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/ WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/ CHENARD