MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 235 PM EDT THU APR 02 2015 VALID APR 02/1200 UTC THRU APR 06/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INITIALIZATION ERRORS WITH THE NAM/GFS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. CLOSED LOW NEAR THE PACIFIC NORTHWEST THIS WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF/CANADIAN COMPROMISE CONFIDENCE: AVERAGE THERE IS A TREND TOWARDS A STRONGER TROUGH ALOFT NEAR THE WEST COAST, WITH THE 12Z ECMWF SHIFTING TOWARDS THE MORE SOUTHERLY 12Z NAM/12Z UKMET SOLUTIONS, AND THE 12Z CANADIAN BECOMING A LITTLE SLOWER WITH ITS PROGRESSION. THE 00Z GLOBAL ENSEMBLE LOW CLUSTERING WAS TIGHT, AND SUPPORTED THE MORE NORTHERN SOLUTIONS -- ECMWF SHIFTS COULD RENDER THE USE OF THE ECMWF ENSEMBLE MEMBERS MOOT. WILL SLOWLY TRANSITION AND PREFER A COMPROMISE OF THE 12Z GFS/12Z ECMWF/12Z CANADIAN WITH AVERAGE CONFIDENCE. SHORTWAVE OVER THE SOUTHWEST REACHING THE PLAINS FRI AM ASSOCIATED COLD FRONT REACHING THE EAST COAST FRI NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE ARE SOME RELATIVELY MINOR SPEED/TRACK ISSUES WITH THIS SYSTEM...WITH THE 00Z NAM SHOWING A SLOWER PROGRESSION WITH THE UPPER TROUGH, SURFACE LOW, AND RELATED COLD FRONT -- ONE OF ITS TYPICAL BIASES. THE 00Z ECMWF/06Z GEFS MEANS SUPPORT A QUICKER 12Z GFS/12Z CANADIAN/12Z ECMWF/12Z UKMET COMPROMISE, WHICH IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. SYSTEM MOVING ACROSS THE NORTH-CENTRAL/NORTHEAST US FRI-SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/UKMET/ECMWF COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM WAS SLOW AND STRONG WITH THIS SYSTEM WHEN COMPARED TO THE OTHER GUIDANCE -- ONE OF ITS USUAL BIASES -- WITH THE 12Z CANADIAN SPEEDING AHEAD OF THE OTHER GUIDANCE. A COMPROMISE OF THE 12Z UKMET/12Z ECMWF/12Z GFS BEST FITS THE 00Z GLOBAL ENSEMBLE LOW CLUSTERING WITH THIS SYSTEM, AND IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. MID-UPPER LEVEL SHORTWAVE REACHING TX SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSE TO THE CANADIAN CONFIDENCE: SLIGHTLY ABOVE AVERAGE THERE ARE DEPTH ISSUES WITH THIS SYSTEM, AS THE 12Z GFS LIES ON THE STRONG SIDE OF THE GUIDANCE WHILE THE 12Z UKMET IS THE WEAKEST -- BOTH FITTING KNOWN BIASES. THE 12Z CANADIAN MADE FOR A NICE COMPROMISE AND IS SLIGHTLY STRONGER THAN THE 00Z ECMWF/06Z GEFS MEAN SOLUTIONS -- NORMALLY A GOOD PLACE TO BE. THE 12Z CANADIAN WAS FAVORED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH