MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1248 AM EDT THU AUG 20 2015 VALID AUG 20/0000 UTC THRU AUG 23/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS APPEAR MINIMAL AND SHOULD NOT DEGRADE SHORT RANGE FORECASTS. STRONG UPPER TROUGH LIFTING INTO SERN CANADA TODAY/FRI AND THE RELATED FRONT THROUGH THE EASTERN STATES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE ARE NO SIGNIFICANT MASS FIELD DIFFERENCES WITH THIS SYSTEM. REGARDING A WEAK FRONTAL WAVE NEAR NEW YORK FRI MORNING...THE MODELS ARE ALL DANCING AROUND A SIMILAR POSITION WITH NO ONE MODEL STANDING OUT OVER ANOTHER. UPPER TROUGH/CYCLONE NEAR THE CENTRAL U.S./CANADIAN BORDER SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z UKMET COMPROMISE CONFIDENCE: AVERAGE THE 12Z ECMWF IS STRONGER ALOFT WITH THIS SYSTEM...AND HAS A MORE SOUTHERLY SURFACE LOW IN MINNESOTA SATURDAY NIGHT...WHICH IS LOCATED ON THE SOUTHERN FRINGE OF THE 12Z ENSEMBLE SPREAD. THE 00Z NAM ON THE OTHER HAND...IS NORTH OF THE REMAINING MODEL MAJORITY...WITH THE 00Z GFS AND 12Z UKMET MATCHING CLOSEST TO THE RELATIVELY TIGHTLY CLUSTERED ENSEMBLE MEANS. MID-UPPER LEVEL DISTURBANCE OVER SOUTH TEXAS...WEAKENING INTO THE WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS GOOD AGREEMENT WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO