MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1129 AM EST WED DEC 30 2015 VALID DEC 30/1200 UTC THRU JAN 03/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS AND PRELIMINARY PREFERENCES CLOSED LOW FORMING OVER THE INTERMOUNTAIN WEST... PREFERENCE: 1/2 EACH GFS/ECMWF CONFIDENCE: AVERAGE THE NAM AND GFS ARE SLIGHTLY NORTH OF THE ECMWF THROUGH THE PERIOD WITH THEIR SOLUTIONS EQUALLY SUPPORTED BY THEIR ENSEMBLES. HOWEVER...THE NAM IS NEAR THE STRONG SIDE OF THE GUIDANCE AND THEREFORE CONSIDERED UNLIKELY AT THIS TIME. SHORTWAVE TROUGH INFLUENCING NEW MEXICO AND TEXAS FRI-SAT... PREFERENCE: 1/2 EACH GFS/ECMWF CONFIDENCE: AVERAGE THE NAM IS NEAR THE STRONG SIDE OF THE GUIDANCE AND THEREFORE CONSIDERED UNLIKELY...WHILE THE GFS/ECMWF ARE MOSTLY SIMILAR. FRONTAL SYSTEM ACROSS THE SOUTHEAST... PREFERENCE: 1/2 EACH GFS/ECMWF CONFIDENCE: AVERAGE THE NAM IS NEAR THE OUTER EDGES OF THE GUIDANCE WITH ITS MORE NORTHWARD PLACEMENT ON SATURDAY...WHICH IS LIKELY A RESULT OF INFLUENCES FROM ITS OUTER EDGES SOLUTIONS OVER THE NORTHEAST AND ACROSS MEXICO. THEREFORE...ITS SOLUTION IS DISCOUNTED...WHILE THE GFS AND ECMWF ARE FARTHER SOUTH AND MOSTLY SIMILAR...INCLUDING WITH THE LINGERING MOISTURE PLUME ACROSS THE GULF. SHORTWAVE TROUGH INFLUENCING THE GREAT LAKES SAT... PREFERENCE: 1/2 EACH GFS/ECMWF CONFIDENCE: AVERAGE THE NAM LIES NEAR THE SLOW AND STRONG SIDES OF THE GUIDANCE AND THUS IS CONSIDERED A LOW PROBABILITY SOLUTION...WHILE THE GFS/ECMWF ARE MORE SIMILAR AND CLOSER TO THE CONSENSUS. THUS...THEIR SOLUTIONS ARE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... JAMES