MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 121 AM EST SUN JAN 18 2015 VALID JAN 18/0000 UTC THRU JAN 21/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION INCLUDING THE UKMET/CANADIAN AND PREFERENCES LOW PRESSURE NEAR THE PACIFIC NORTHWEST COAST... PREFERENCE: GFS OR ECMWF CONFIDENCE: ABOVE AVERAGE MODEL LOW TRACKS ARE SIMILAR. HOWEVER...THE NAM/UKMET ARE ON THE MORE AMPLIFIED SIDE OF THE GUIDANCE ALOFT...WHICH MAY HELP TO EXPLAIN THEIR WETTER SOLUTIONS ON DAY 1. GIVEN STRONGER SUPPORT FOR THE WEAKER GFS/ECMWF SOLUTIONS...THE PREFERENCE IS FOR EITHER THE GFS OR ECMWF. LOW PRESSURE MOVING FROM THE DAKOTAS TO THE OH VALLEY MON-TUE... PREFERENCE: EQUAL BLEND GFS/ECMWF CONFIDENCE: AVERAGE THE NAM LIES NEAR THE STRONG EDGE OF THE GUIDANCE ALOFT CROSSING THE PACIFIC NORTHWEST WHICH CONTRIBUTES TO A MORE NORTHERN LOW TRACK ACROSS THE MIDWEST AND OH VALLEY. THUS...ITS RESULTING LOWER LEVEL WINDS AND THERMAL PROFILES ARE NOT RECOMMENDED. ON A LARGER SCALE...THE NAM DRIFTS BACK TOWARD THE CONSENSUS ALOFT BY 84 HRS. THUS...SOME OF ITS ASSOCIATED ASCENT FIELDS BY DAY 3 MAY BE RELIABLE. AMONG THE REMAINING SOLUTIONS...THE GFS/ECMWF ARE CLOSE TO THE MODEL CONSENSUS...AND HAVE GOOD SUPPORT FROM THE ENSEMBLE MEANS. GIVEN THE LARGE SPREAD THAT DEVELOPS BY DAY 3 HOWEVER...AN EQUAL BLEND OF THE GFS/ECMWF IS PREFERRED. LOW PRESSURE OVER NEW ENGLAND SUNDAY NIGHT-MONDAY... THE 00Z UKMET/CANADIAN/ECMWF HAVE ALL TRENDED TOWARD AND ARE NOW IN GOOD AGREEMENT WITH THE LOW TRACKS AND DEPTH OF THE NAM/GFS...WITH ONLY MINOR DIFFERENCES REMAINING. REFER TO THE QPFHSD FOR MORE INFORMATION ON WINTER WEATHER. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... JAMES