MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1218 AM EDT SUN AUG 09 2015 VALID AUG 09/0000 UTC THRU AUG 12/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...UPPER TROUGHING IMPACTING NEW ENGLAND THROUGH SUN... ...SURFACE LOWS EXITING OFF THE EAST COAST... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE THE 00Z NAM IS A LITTLE SLOWER AND DEEPER THAN THE GLOBAL MODELS WITH THIS SYSTEM. A NON-NAM CONSENSUS WILL BE PREFERRED. ...UPPER TROUGH CROSSING THE NORTHERN PLAINS/MIDWEST THROUGH MON... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE NO SIGNIFICANT DIFFERENCES WERE NOTED WITH THIS SYSTEM SO A GENERAL MODEL COMPROMISE IS PREFERRED. ...UPPER TROUGH/CLOSED LOW CURRENTLY OVER SOUTHERN CANADA... ...ENERGY AMPLIFYING INTO THE GREAT LAKES/NORTHEAST THROUGH TUES... ...SURFACE LOW LIFTING FROM THE PLAINS/MIDWEST TO THE NORTHEAST... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE SREF/GEFS/ENSEMBLE MEANS SHOW VERY GOOD AGREEMENT THROUGH TUES AND INTO WED WITH THE EVOLUTION OF A LARGE SCALE UPPER TROUGH FORECAST TO DEVELOP OVER THE NORTHEASTERN QUADRANT OF THE U.S. AND WITH THE TRACK OF A SURFACE LOW FROM THE MIDWEST ON MON TO INTERIOR NEW ENGLAND BY WED. THE 00Z GFS AND 12Z ECMWF ARE CLOSEST TO THE MEANS AT ALL TIMES. THE 00Z NAM TENDS TO BE A BIT SLOWER THAN THE GLOBAL MODEL CONSENSUS WITH THE SURFACE LOW AND IS A BIT DEEPER WITH THE TROUGH ALOFT. THE 12Z UKMET ALSO TENDS TO BE A SLOWER WITH THE SURFACE LOW. THE 12Z CMC SHOWS STRONGER SUPPORT FOR THE GFS/ECMWF CLUSTER...AND SO A BLEND OF THE 00Z GFS AND 12Z ECMWF WILL BE PREFERRED. ...UPPER TROUGH DIGGING DOWN OFF THE WEST COAST THIS WEEKEND... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT IN TAKING AN UPPER LOW SOUTH FROM JUST OFFSHORE BRITISH COLUMBIA DOWN TO OFFSHORE THE WEST COAST OVER THE NEXT FEW DAYS. THERE ARE SOME MINOR PLACEMENT DIFFERENCES WITH THE UPPER LOW...BUT IN GENERAL THE MODELS ARE REASONABLY WELL CLUSTERED AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON