MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1240 AM EDT TUE AUG 26 2014 VALID AUG 26/0000 UTC THRU AUG 29/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...UPPER LOW EXITING THROUGH SOUTHERN CANADA THROUGH TUES... ...TRAILING COLD FRONT... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE AGAIN SHOWS VERY GOOD AGREEMENT WITH THE DEPARTURE OF THE UPPER LOW AND ASSOCD SFC LOW INTO CANADA THROUGH TUES MORNING. THERE IS MINIMAL SPREAD TOO WITH THE TRAILING COLD FRONT THAT CROSSES THE GREAT LAKES REGION AND MOVES INTO THE NORTHEAST TUES NIGHT AND WED. A GENERAL MODEL COMPROMISE WILL AGAIN BE PREFERRED. ...MID LEVEL SHORTWAVE/CLOSED LOW DIGGING ADVANCING ACROSS THE WEST... ...WEAK SURFACE LOW OVER THE CENTRAL PLAINS/MIDWEST BY FRI... PREFERENCE: BLEND OF THE 12Z GEM AND 12Z ECMWF CONFIDENCE: ABOVE AVERAGE THE MODELS REMAIN IN VERY GOOD AGREEMENT AT LEAST ON THE LARGE SCALE IN ALLOWING AN UPR TROUGH AND ASSOCD CLOSED LOW TO ADVANCE EAST THROUGH THE GRT BASIN AND THEN CROSS THE CNTRL ROCKIES ON ITS WAY OUT INTO THE PLAINS THROUGH THURS AND FRI. SOME DIFFS SHOW UP BY THURS AND INTO FRI AS THE 00Z NAM CONCENTRATES A LITTLE MORE OF ITS ENERGY/HEIGHT FALLS FARTHER NORTH AS COMPARED TO THE 12Z ECMWF/12Z GEM AND 00Z GFS WHICH ALL HAVE A CLOSED LOW OVER SERN CO/WRN KS. THE 12Z UKMET HAS A CLOSED LOW AS WELL BUT IT IS A TAD WEAKER WITH IT. THE 00Z NAM WITH ITS ENERGY A LITTLE FARTHER NORTH ALSO SENDS A WEAK SFC LOW A LITTLE FARTHER OFF TO THE NORTHEAST UNTIL LATE IN THE PERIOD WHEN THE 00Z GFS ARRIVES HERE AND BECOMES A LITTLE FASTER THAN THE 00Z NAM. THE NON-NCEP SOLNS ARE ALL A LITTLE SLOWER. THE ONE CONCERN AT THE SFC WITH THE GFS IS SOME CONVECTIVE FEEDBACK...AND SO THE GFS WILL NOT BE PREFERRED. THE STRONGER MODEL CLUSTERING FAVORS THE 12Z GEM AND 12Z ECMWF OVERALL...AND THIS WILL BE THE PREFERENCE. ...SHORTWAVE TROUGH DIGGING INTO THE NORTHEAST THROUGH THURS AND FRI... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE A NORTHERN STREAM TROUGH IS EXPECTED TO DIG ACROSS THE ST LAWRENCE RIVER VLY ON WED AND INTO THE NORTHEAST ON THURS. THE MODELS ARE WELL CLUSTERED WITH THE TIMING AND DEPTH OF THIS ENERGY...WITH EXCEPTION OF THE 00Z NAM WHICH AGAIN IS A SLOWER AND DEEPER OUTLIER SOLN. WILL BE FAVORING A NON-NAM CONSENSUS AS A RESULT. ...NORTHERN STREAM TROUGH CLIPPING THE U.S./CANADIAN BORDER BY FRI... PREFERENCE: 12Z ECMWF CONFIDENCE: ABOVE AVERAGE A NRN STREAM TROUGH WILL BE CLIPPING THE NRN TIER STATES THURS INTO FRI. THE 00Z GFS IS A TAD SLOWER WITH THIS ENERGY...AND ESP ITS SFC LOW REFLECTION HERE. THE 12Z UKMET IS THE MOST PROGRESSIVE SOLN...WITH THE REMAINING MODELS SPLITTING THE DIFF. WILL BE PREFERRING THE 12Z ECMWF. ...DEEP TROUGH DIGGING JUST OFF THE NORTHWEST BY FRI... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 00Z NAM IS A TAD STRONGER THAN THE GLOBAL MODEL CONSENSUS WITH THE UPR TROUGH DIGGING THROUGH THE GULF OF AK AND OFFSHORE THE NORTHWEST THURS AND FRI. THE GLOBAL MODELS ARE REASONABLY WELL CLUSTERED...WITH THE 00Z GFS AND THE 12Z ECMWF MORE STRONGLY ALIGNED. WILL PREFER A BLEND OF THE GFS AND ECMWF ATTM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON