MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1123 AM EST WED DEC 09 2015 VALID DEC 09/1200 UTC THRU DEC 13/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES LOW PRESSURE NEARING THE PACIFIC NORTHWEST SATURDAY... PREFERENCE: 1/3 EACH NAM/00Z ECMWF ALONG WITH AN ENSEMBLE MEAN CONFIDENCE: AVERAGE THE GFS IS UNUSUALLY FAST AND DEEP GIVEN THE PRECEDING RIDGE AND ITS STRENGTH OVER THE REGION...WHILE THE NAM IS IN PHASE WITH THE 00Z ECMWF AND THE ENSEMBLE MEANS...EXCEPT SLIGHTLY STRONGER WHICH MIGHT BE USEFUL TO CONSIDER GIVEN THE ENSEMBLE MEMBER SPREAD. OVERALL...RECOMMEND A 3-WAY BLEND OF THE NAM/00Z ECMWF ALONG WITH AN ENSEMBLE MEAN. UPPER TROUGH FORMING OVER THE SOUTHWEST THIS WEEKEND... FRONTAL SYSTEM OVER THE PLAINS/OH VALLEY... PREFERENCE: 1/4 EACH NAM/00Z ECMWF/06Z GEFS MEAN/00Z ECMWF ENSEMBLE MEAN CONFIDENCE: AVERAGE THE GFS IS UNUSUALLY FAST WITH AN UPSTREAM SHORTWAVE TROUGH REACHING THE PACIFIC NORTHWEST ON DAY 3 THAT HELPS TO EJECT THE UPPER TROUGH INTO THE ROCKIES PERHAPS TOO QUICKLY...AND IS ALSO STRONGER WITH LOW PRESSURE CROSSING THE GREAT LAKES...WHICH HELPS THE WARM FRONT OVER THE OH VALLEY TO REMAIN SOUTH OF THE MODEL CONSENSUS. GIVEN THESE DIFFERENCES...RECOMMEND DISCOUNTING THE GFS. MEANWHILE...THE NAM AGREES IS MOST AREAS WITH THE 00Z ECMWF...EXCEPT MAY BE A LITTLE NORTH OF THE ECWMF'S WARM FRONT OVER THE OH VALLEY...WITH THE MORE NORTHERN POSITION PREFERRED GIVEN SUPPORT OF THE ENSEMBLES AND SOME CONCERNS WITH THE ECMWF'S LOW TRACK ACROSS THE GREAT LAKES EARLIER. WITHIN THE UPPER TROUGH ITSELF...THE ENSEMBLE MEANS ARE BETWEEN THE NAM/ECMWF. LOW PRESSURE INFLUENCING THE UPPER MIDWEST THURSDAY... PREFERENCE: NAM OR GFS CONFIDENCE: ABOVE AVERAGE THE NAM AND GFS HAVE TRENDED FASTER AND SHOW GOOD AGREEMENT WITH EACH OTHER WITH A MORE NORTHERN LOW TRACK VERSUS THE 00Z ECMWF WHICH HAS TRENDED WEAKER AND NORTH TOWARD THE NAM/GFS. THUS...RECOMMEND EITHER THE NAM OR GFS. LOW PRESSURE INFLUENCING THE N-CENTRAL PLAINS/UPPER MIDWEST FRIDAY. PREFERENCE: NAM OR 00Z ECMWF CONFIDENCE: ABOVE AVERAGE THE GFS IS A DEEP OUTLIER AND FITS POORLY WITH THE CONFLUENT FLOW DOWNSTREAM INTO THE RIDGE. THUS...RECOMMEND DISCOUNTING THE GFS IN FAVOR OF EITHER THE NAM OR 00Z ECMWF WHICH SHOW GOOD AGREEMENT WITH EACH OTHER. WARM FRONT AFFECTING THE NORTHEAST/NEW ENGLAND TONIGHT/THURSDAY... MODELS SHOW GOOD LARGE-SCALE AGREEMENT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... JAMES