MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1246 PM EDT SAT JUL 19 2014 VALID JUL 19/1200 UTC THRU JUL 23/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES SHORTWAVE TROUGH LIFTING THROUGH THE TN/OH VALLEYS INTO THE NORTHEAST WEAK MID-LEVEL DISTURBANCE LEFT BEHIND OVER THE SOUTHEAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF AND 00Z UKMET CONFIDENCE: A LITTLE BELOW AVERAGE THE MID LEVEL SHORTWAVE OVER THE OH/TN VLYS ATTM WILL LIFT INTO THE NORTHEAST THIS WEEKEND...ALTHOUGH THERE IS EXPECTED TO BE A BROAD AND WEAK TROUGH LEFT BEHIND IN ITS WAKE OVER THE TN VLY AND MUCH OF THE SOUTHEAST SUN THROUGH TUE. MOST OF THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE TIMING AND DEPTH OF EVOLVING MASS FIELDS...BUT THE 12Z NAM WAS NOTED TO BE A LITTLE STRONGER THAN THE GLOBAL MODEL CONSENSUS WITH THE LINGERING ENERGY OVER THE SOUTHEAST. THE 12Z GFS IS SECOND STRONGEST WHILE THE 00Z ECMWF/UKMET ARE WEAKER AND AABOUT 300 MILES EAST WITH THE 700 MB CIRCULATION OVER THE SOUTHEAST TUE EVENING. THE 00Z CMC APPEARS TO BE THE OUTLIER OF THE DETERMINISTIC BUNCH WITH A FASTER PROGRESSION OF THE UPPER TROUGH TOWRAD THE EAST COAST. WE WILL FAVOR A BLEND OF THE GFS/ECMWF AND UKMET. UPPER TROUGH/COLD FRONT CLIPPING THE NORTHERN U.S SUN AND MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT AT LEAST ON THE LARGER SCALE WITH THIS SYSTEM...SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED TO RESOLVE THE SMALLER SCALE DIFFS. DEEP UPPER TROUGH/CLOSED LOW DEVELOPING OVER THE GULF OF AK AND IMPACTING THE NORTHWEST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE OVERALL...THERE IS REASONABLY GOOD MASS FIELD AGREEMENT AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED TO RESOLVE THE SMALLER SCALE DIFFS. WEAK MID/UPPER LEVEL LOW WEAKENING NWD FROM SRN CALIFORNIA TODAY SURFACE LOW DEVELOPING FROM THE NRN PLAINS BY MON AND TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS / 00Z ECMWF CONFIDENCE: AVERAGE THE MODELS SUGGEST THAT THE UPPER LOW CURRENTLY OVER THE NRN BAJA PENINSULA WILL LIFT NWD WHILE WEAKENING THIS WEEKEND...WHILE A PIECE OF THE UPPER TROUGH RIDES OVER A STRONG RIDGE CENTERED OVER THE SRN HIGH PLAINS...REACHING THE NRN PLAINS MON EVENING. THIS SHORTWAVE SHOULD ALLOW FOR THE DEVELOPMENT OF A SURFACE LOW IN SOUTH DAKOTA WITH A TRAILING COLD FRONT. THE GFS AND ECMWF REPRESENT A COMPROMISE OF MODEL SOLUTIONS THAT BEST FITS THE MIDDLE OF THE DETERMINITIC/ENSEMBLE SPREAD...WITH DECENT RUN TO RUN CONTINUITY. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO