MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1258 PM EDT MON AUG 15 2016 VALID AUG 15/1200 UTC THRU AUG 19/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION ALONG WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ MID-UPPER LEVEL TROUGH LIFTING OUT OF THE SRN/CNTRL PLAINS TONIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS...00Z ECMWF...00Z UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE GENERALLY GOOD AGREEMENT EXISTS WITH THE MID-UPPER LEVEL WAVE UNTIL TUE EVENING WHEN THE 00Z CMC FALLS BEHIND THE REMAINING MODEL CONSENSUS. OVERALL...THE 12Z NAM WAS ON THE NRN END OF THE DETERMINISTIC CONSENSUS...WHILE THE 00Z CMC WAS SOUTH OR WEST OF THE BETTER ENSEMBLE CLUSTERING OF SURFACE LOW POSITIONS. THE 12Z GFS/00Z ECMWF/00Z UKMET FORM A GOOD COMPROMISE. AMPLIFYING FLOW ACROSS THE NORTH-CENTRAL U.S. THROUGH TUESDAY MID-UPPER TROUGH AXIS PASSING ACROSS THE GREAT LAKES WED NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF CONFIDENCE: AVERAGE THE GREATEST MODEL DIFFERENCES NOTED WITH THIS SYSTEM WERE ACROSS PARTS OF LOWER MICHIGAN WED EVENING WHERE THE 12Z NAM IS STRONGER THAN THE CONSENSUS. THE 00Z ECMWF HAS BEEN TRENDING STRONGER OVER ITS PAST 3 RUNS AND THE GFS HAS OSCILLATED BETWEEN WEAKER AND STRONGER...WITH THE 12Z GFS WEAKER AGAIN. GIVEN SIMILAR AMPLIFICATION OF AN UPSTREAM WAVE...A BLEND REPRESENTING THE TWO CAMPS IS RECOMMENDED...BEST SHOWN BY A BLEND OF THE 12Z GFS AND 00Z ECMWF. WEAK MID-LEVEL IMPULSES IMPACTING LOCATIONS FROM CA TO THE CNTRL ROCKIES WITHIN A BROAD UPPER TROUGH ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z NAM BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE A PAIR OF SHORTWAVES WILL TRACK FROM NORTHERN CA TOWARD THE CENTRAL GREAT BASIN/ROCKIES THROUGH LATE THU. THERE IS GENERAL AGREEMENT WITH SMALLER SCALE DETAIL DIFFERENCES WITH HOW THESE FEATURES EVOLVE...BUT THE 12Z NAM STANDS OUT WITH DEEPER MID-LEVEL TROUGHING INTO THE SRN PLAINS THU EVENING. GIVEN A LACK OF SUPPORT FOR THE NAM...A NON 12Z NAM BLEND IS PREFERRED. AMPLIFYING UPPER TROUGH OVER S-CNTRL CANADA BY THU SURGING COLD FRONT IMPACTING THE NRN PLAINS THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS/00Z UKMET CONFIDENCE: AVERAGE WHILE THE 00Z UKMET IS MORE AMPLIFIED ACROSS CNTRL CANADA...THE GFS/ECMWF/UKMET ARE IN GOOD AGREEMENT ACROSS THE LOWER 48 UNTIL LATE THU WHEN THE 00Z ECMWF SURFACE LOW IN THE N-CNTRL U.S. EDGES EAST OF THE LATEST ENSEMBLE CLUSTERING. BETTER CLUSTERING EXISTS FOR A BLEND OF THE 12Z GFS AND 00Z UKMET REGARDING TIMING AND STRENGTH OF THE COLD FRONT AND SURFACE WAVE. OTTO www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...