MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1225 AM EDT TUE APR 01 2014 VALID APR 01/0000 UTC THRU APR 04/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SHARP TROUGH ENTERING THE WEST COAST THU NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS GOOD AGREEMENT WITH THIS SYSTEM. A GENERAL MODEL COMPROMISE IS PREFERRED TO DEAL WITH ANY LINGERING DETAIL ISSUES WITH ABOVE AVERAGE CONFIDENCE CONSIDERING THE MINIMAL SPREAD SEEN IN THE DETERMINISTIC/ENSEMBLE MEAN GUIDANCE. DEEP CYCLONE MOVING INTO THE PLAINS/MIDWEST THU & FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/GFS COMPROMISE CONFIDENCE: AVERAGE THERE IS SOMEWHAT ABOVE AVERAGE MODEL SPREAD WITH THIS SYSTEM, WITH THE 00Z NAM/12Z UKMET SPEEDING ALONG -- FITTING A KNOWN UKMET BIAS WITH SYSTEMS IN THE WESTERLIES -- LEAVING THE EAST SIDE OF THE 12Z GLOBAL ENSEMBLE SPREAD FRIDAY MORNING. THE 12Z CANADIAN IS ON THE SLOW SIDE OF THE GUIDANCE, THOUGH IT WAS TRENDED QUICKER WITH THIS SYSTEM OVER ITS PAST COUPLE DAYS OF RUNS. THE GENERAL FLOW PATTERN REMAINS PROGRESSIVE, WITH A KICKER SHORTWAVE ENTERING STAGE LEFT FROM THE PACIFIC THURSDAY NIGHT. PER THE ABOVE, THE SLOWER CANADIAN SOLUTION IS LIKELY TOO SLOW. TWO-DAY MODEL TRENDS IN THE GFS/ECMWF ARE REVEALING, WITH THE ECMWF SHOWING A WEAKENING TREND ALOFT/SOUTHERLY TREND WITH ITS MAIN SURFACE LOW AND SLOWING TREND WITH ITS TRAILING SURFACE FRONT, WHILE THE GFS HAS TRENDED SOMEWHAT QUICKER AND MORE NORTHERLY WITH ITS LOW TRACK AND RELATED FRONTAL STRUCTURE/ZONES. ANOTHER AREA OF UNCERTAINTY (DETAIL-WISE) LIES FROM THE CENTRAL APPALACHIANS EASTWARD, WHERE MUCH OF THE GUIDANCE SHOWS A SHORTWAVE (CONVECTIVE OR OTHERWISE) MOVING A WEAK FRONTAL WAVE ALONG THE SOUTHERN EDGE OF A COLD AIR WEDGE AT VARYING INTENSITIES AND SPEEDS. THE BEST 12Z GLOBAL ENSEMBLE CLUSTERING WITH THE MAIN SURFACE LOW LIES BETWEEN THE GFS/ECMWF SOLUTIONS. KEEPING THE ABOVE IN MIND, A COMPROMISE OF THE 12Z ECMWF/00Z GFS APPEARS BEST HERE, WITH CONFIDENCE AVERAGE SINCE THE GUIDANCE APPEARS TO BE SLOWLY TRENDING TOWARDS A COMMON SOLUTION. FRONT MOVING THROUGH THE NORTHEAST WED & THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE HANDLES THE CYCLONE MOVING OUT OF MN/WI/MI REASONABLY WELL AS IT MOVES INTO SOUTHEAST CANADA, WHICH TRANSLATES TO A REASONABLY SIMILAR FRONTAL PROGRESSION. A GENERAL MODEL COMPROMISE IS PREFERRED TO DEAL WITH ANY LINGERING DETAIL ISSUES WITH THE SYSTEM, WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... ROTH