MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1226 PM EDT THU SEP 10 2015 VALID SEP 10/1200 UTC THRU SEP 14/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES SHORTWAVE TROUGH INFLUENCING CALIFORNIA/SOUTHWEST THIS WEEKEND... PREFERENCE: CONSENSUS CONFIDENCE: AVERAGE MODELS DEPICT A SIMILAR LARGE-SCALE EVOLUTION AS THE TROUGH NEARS THE COAST AND ENTRAINS REMNANT MOISTURE FROM LINDA. RECOMMEND A CONSENSUS APPROACH TO RESOLVE ANY SMALL-SCALE UNCERTAINTIES. COLD FRONT EXTENDING FROM THE UPPER MIDWEST INTO THE PLAINS... LOW PRESSURE FORMING ALONG THE EAST COAST THIS WEEKEND... PREFERENCE: BEFORE 00Z SUN...NAM OR GFS AFTER 00Z SUN...1/3 EACH 12Z GFS/06Z GEFS MEAN/00Z ECMWF ENSEMBLE MEAN CONFIDENCE: BEFORE 00Z SUN...AVERAGE AFTER 00Z SUN...LOW FRONTAL STRENGTH AND TIMING ARE SIMILAR AMONG THE GUIDANCE. DIFFERENCES BECOMING INCREASINGLY APPARENT HOWEVER AS THE FRONT SLOWS ALONG THE EAST COAST...WITH THE NAM/GFS TRENDING FASTER AND WEAKER WITH THE LOW COMPARED TO THE SLOWER/STRONGER 00Z ECMWF...PARTICULARLY WITH THE NORTHERN STREAM. RECENT TRENDS AND A CONSENSUS OF THE ENSEMBLE MEANS FAVOR A SOLUTION RELATIVELY CLOSE TO THE 12Z GFS....WHICH IS SLOWER THAN THE NAM AND FASTER/WEAKER THAN THE 00Z ECMWF. GIVEN THE SPREAD HOWEVER...RECOMMEND BLENDING THE GFS WITH THE ENSEMBLE MEANS BY DAY 3...WITH DECREASING CONFIDENCE BY DAY 3. SHORTWAVE TROUGH EXTENDING ALONG THE APPALACHIANS... PREFERENCE: GFS OR 12Z ECMWF CONFIDENCE: ABOVE AVERAGE THE NAM'S ACCOMPANYING LOW TRACK IS WEST OF THE CONSENSUS WITH ITS CONUS NEST RUN ACTUALLY CLOSER TO THE GFS AND 12Z ECMWF. THUS...RECOMMEND THE GFS OR ECMWF. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... JAMES