MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1248 AM EDT WED JUL 20 2016 VALID JUL 20/0000 UTC THRU JUL 23/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z PRELIMINARY MODEL EVALUATION AND PREFERENCES ...SHORTWAVE ENERGY MOVING EAST ACROSS SOUTHERN CANADA...EVENTUALLY INTO THE TROUGH OVER NEW ENGLAND... PREFERENCE: 0Z GFS AND 12Z ECMWF BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE SHORTWAVE ENERGY EJECTING EAST OUT OF THE PACIFIC NORTHWEST TROUGH IS EXPECTED TO MOVE ACROSS SOUTEHRN CANADA THROUGH THE WEEK...TOWARDS NORTHERN NEW ENGLAND ON FRIDAY. THE 0Z GFS AND 12Z ECMWF HAVE COME INTO VERY GOOD AGREEMENT ON THE EVOLUTION OF THESE FEATURES. THE 0Z NAM IS A SLOW OUTLIER AND REPRESENTS A LESS LIKELY SOLUTION. THE 12Z UKMET ALSO APPEARS TO BE STRUGGLING WITH THE HANDLING OF THE SHORTWAVES. THE 12Z GEM IS OKAY...BUT SEEMS TO BE SLIGHTLY LAGGING THE TRENDS SEEN IN THE GFS AND ECMWF. ...PACIFIC NORTHWEST TROUGH AND INITIAL CLOSED LOW...SHORTWAVE EJECTING FROM WA INTO MT/ND BY 12Z SATURDAY... PREFERENCE: 0Z GFS AND 12Z ECMWF BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE SYNOPTIC SET-UP OF THIS FEATURE WITH THE CLOSED LOW JUST WEST OF THE WASHINGTON COAST EVOLVING INTO AN OPEN WAVE WITH SMALLER SCALE SHORTWAVE DISTURBANCES ROTATING AROUND IT. BY THURSDAY NIGHT A STRONGER LOBE OF SHORTWAVE ENERGY IS EXPECTED TO MOVE ASHORE...AND TRACK ACROSS ID/MT THROUGH FRIDAY. MODEL SPREAD DOES BEGIN TO INCREASE SOME BY THAT POINT...WITH THE NAM/GFS MORE PROGRESSIVE THAN THE NON NCEP MODELS. THE 0Z NAM APPEARS TO OUTRUN THE BETTER MODEL CLUSTERING AND IS CONSIDERED A LESS LIKELY SOLUTION. FEEL THE MOST LIKELY OUTCOME AT THIS TIME IS SOMEWHERE BETWEEN THE 0Z GFS AND 12Z ECMWF...THUS WILL RECOMMEND A BLEND OF THESE SOLUTIONS. ...LARGE UPPER LEVEL RIDGE OVER THE CENTRAL U.S.... PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE ON THE RIDGE, AND BELOW AVERAGE ON SHORTWAVE IMPULSES OVERALL VERY GOOD AGREEMENT IN THE MAINTENANCE OF A LARGE 594 DM 500 MB RIDGE OVER THE CENTRAL AND SOUTHERN US. THE 0Z NAM IS LIKELY A BIT QUICK IN BREAKING DOWN THE RIDGE. SOME DIFFERENCES ON THE SUBTLE SHORTWAVE FEATURES THAT WILL LIKELY TRAVEL ALONG THE PERIPHERY OF THIS RIDGE THROUGH THE PERIOD. SEE THE QPFPFD FOR MORE DETAILS ON THESE SUBTLE SHORTWAVES AND POSSIBLE ASSOCIATED CONVECTION. CHENARD www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...