MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 245 AM EDT FRI APR 03 2015 VALID APR 03/0000 UTC THRU APR 06/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL 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: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THE 00Z NAM IS A LITTLE SLOWER THAN THE LATEST CONSENSUS WITH A SHORTWAVE AT THE BASE OF THE TROUGH NEARING THE NRN CALIFORNIA COAST SUN MORNING BUT THERE IS OTHERWISE PRETTY GOOD AGREEMENT IN THE MODELS. INDIVIDUAL SHORTWAVE DETAILS COMPLICATE THE EVOLUTION OF THE TROUGH MOVING INLAND BY MON MORNING...WITH A FAIR DEGREE OF ENSEMBLE SPREAD. HOWEVER...THE LATEST 00Z MODLE SUITE SHOWS FARILY GOOD AGREEMENT THROUGH MON MORNING WITH PLACEMENT TOWARD THE MIDDLE OF THE LATEST ENSEMBLE SPREAD. SHORTWAVE REACHING THE NRN APPALACHIANS FRI NIGHT AND THE ASSOCIATED COLD FRONT REACHING THE EAST COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z 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 BY FRI NIGHT. THE REMAINING 00Z GUIDANCE IS QUICKER THAN THE NAM...WITH WHILE THE 00Z CMC IS FASTEST...IT HAS SLOWED FROM ITS PREVIOUS RUN TO AN ACCEPTABLE RANGE GIVEN THE LATEST ENSEMBLE GUIDANCE. COLD FRONT MOVING ACROSS THE N-CNTRL U.S./GREAT LAKES SAT/SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF/UKMET/CMC CONFIDENCE: AVERAGE THE ENSEMBLE SCATTER LOW PLOTS SUPPORT A POSITION OF THIS BOUNDARY AND A FRONTAL WAVE TRACKING ENEWD ACROSS THE GREAT LAKES SUN/SUN NIGHT CLOSE TO THE 12Z ECMWF. THE 00Z NAM/GFS APPEAR TO BE SOUTH OF THE BETTER ENSEMBLE SUPPORT...WITH THE 00Z ECMWF/UKMET/CMC HAVING BETTER AGREEMENT HERE. MID-UPPER LEVEL SHORTWAVE REACHING CNTRL/SRN PLAINS SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF/CMC COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE THE MODELS SHOW SIMILAR IDEAS...DESPITE CONVECTIVE DETAIL DIFFERENCES...WITH THE TRACK/DEPTH OF A MID-UPPER LEVEL SHORTWAVE EXPECTED TO REACH THE CNTRL/SRN PLAINS ON SUNDAY. TRENDS SUPPORT A WEAKER AND FASTER WAVE THAN DEPICTED BY THE 00Z NAM...BUT THE 00Z UKMET REMAINS UNSUPPORTED WITH A MUCH FLATTER/FASTER WAVE. THIS IS A SIGNIFICANT CHANGE FROM EARLIER/SLOWER UKMET SOLUTIONS. THE 00Z GFS/ECMWF/CMC SHOW REASONABLE AGREEMENT ALTHOUGH THE GFS IS A BIT SLOWER/AMPLIFIED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO