MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1120 PM EST SUN JAN 18 2015 VALID JAN 19/0000 UTC THRU JAN 22/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES LOW PRESSURE OVER NEW ENGLAND... MODELS SHOW GOOD AGREEMENT WITH THE TRACK AND STRENGTH OF THE LOW. SERIES OF LOW PRESSURE AREAS MOVING FROM THE UPPER MIDWEST TO THE OH VALLEY THROUGH WED... PREFERENCE: EQUAL BLEND GFS/12Z ECMWF CONFIDENCE: AVERAGE THE NAM IS FAIRLY CLOSE TO THE MODEL CONSENSUS THROUGH MONDAY NIGHT BEFORE GRADUALLY MOVING TOWARD THE SLOW/DEEP/NORTHERN SIDES OF THE GUIDANCE WITH THE SERIES OF LOWS...WHICH IN PART APPEARS TO BE AN ACCUMULATION OF SMALL DIFFERENCES FROM THE OTHER SOLUTIONS. OVERALL...THE SOLUTION SPREAD GROWS QUICKLY...WITH AN EQUAL BLEND OF THE GFS/12Z ECMWF MOST REPRESENTATIVE OF THE CONSENSUS WHILE ALSO PROVIDING DETERMINISTIC DETAIL. LOW PRESSURE FORMING NEAR THE MID-ATLANTIC/NORTHEAST COAST WED NGT... PREFERENCE: GFS OR 12Z ECMWF CONFIDENCE: AVERAGE THE NAM REPRESENTS THE WESTERN EDGE OF THE GUIDANCE AND IS LEAST PREFERRED DUE TO ITS UNDESIRABLE UPSTREAM SOLUTION CROSSING THE OH VALLEY AND APPALACHIANS. MEANWHILE...THE GFS AND 12Z ECMWF ARE CLOSE TO THE CONSENSUS...INCLUDING THE ENSEMBLE MEANS...WHICH IS MOST PREFERRED DUE TO THE GROWING SOLUTION SPREAD. SHORTWAVE TROUGH INFLUENCING THE SOUTHWEST WED-WED NGT... PREFERENCE: 3/4 12Z ECMWF TO 1/4 GFS CONFIDENCE: AVERAGE THE NAM LIES NEAR THE NORTHERN SIDE OF THE GUIDANCE WITH THE FORCING MECHANISMS REACHING THE SOUTHERN ROCKIES AND HIGH PLAINS LATE IN THE PERIOD...WHICH IN PART IS DUE TO ITS SLOWER SOLUTION CROSSING THE NORTHERN AND CENTRAL ROCKIES. MEANWHILE...THE GFS/12Z ECMWF ARE CLOSE TO THE CONSENSUS FOR PHASE. HOWEVER...THE GFS LIES NEAR THE STRONG EDGE OF THE GUIDANCE. GIVEN THE SPREAD...RECOMMEND LEANING TOWARD THE ECMWF SOLUTION...WITH ONLY MINOR CONTRIBUTIONS FROM THE GFS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... JAMES