MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 240 AM EDT SAT APR 23 2016 VALID APR 23/0000 UTC THRU APR 26/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM INITIALIZATION ERRORS APPEAR NEGLIGIBLE WITH RESPECT TO THEIR FORECASTS. UPPER LEVEL TROUGH REACHING THE SRN PLAINS EARLY SUN MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW ONLY MINOR MASS FIELD DIFFERENCES WITH THIS SYSTEM. CLOSED LOW REACHING THE NORTHERN HIGH PLAINS SUNDAY MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/00Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE SURFACE LOW IN THE 00Z NAM IS ON THE NORTH SIDE OF THE DETERMINISTIC AND ENSEMBLE SPREAD BY SUN AFTERNOON ACROSS SOUTH DAKOTA...WHILE THE 00Z UKMET/CMC REMAIN ON THE SLOWER/WRN EDGE OF THE MODEL SPREAD. RUN TO RUN CONSISTENCY IN THE GEFS/ECMWF ENSEMBLES HAS BEEN GOOD AND SUPPORTS A SURFACE POSITION BETWEEN THE 00Z GFS AND 12Z ECMWF. THE 00Z ECMWF ADJUSTED NORTH A BIT BUT IT IS WITHIN THE NOISE OF RUN TO RUN ADJUSTMENTS. REGARDING LOWER TO UPPER LEVEL HEIGHT FIELDS...THERE ARE RELATIVELY MINOR DIFFERENCES WITH THE ENSEMBLE MEANS SUPPORTING PLACEMENT OF A GFS/ECMWF BLEND. SYSTEM MOVING INTO THE PACIFIC NORTHWEST ON SUNDAY AND DEVELOPING INTO A CLOSED LOW OVER THE GREAT BASIN FOR MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF/UKMET COMPROMISE CONFIDENCE: AVERAGE GIVEN THE ANOMALOUS UPPER RIDGE IN PLACE OVER WRN CANADA...AN UPPER TROUGH APPROACHING THE PACIFIC NORTHWEST ON SUNDAY IS FORCED TO DROP SOUTH INTO THE GREAT BASIN WHILE CLOSING OFF. THERE IS GOOD MODEL AGREEMENT FOR THIS SCENARIO...BUT SOME MINOR TIMING DIFFERENCES APPEAR BY TUE MORNING. THE CUT OFF NATURE OF THE SYSTEM SUPPORTS A SOMEWHAT SLOWER EWD PROGRESSION OF THE CLOSED LOW TOWARD THE CNTRL ROCKIES...AND THE 12Z ECMWF IS ON THE FASTER SIDE OF THE MODEL SPREAD...WITH ITS OWN ENSEMBLE MEAN SUPPORTING A SLOWER TRACK. THE 00Z ECMWF SLOWED DOWN A BIT...WHILE THE 00Z CMC SPED UP FROM ITS 12Z CYCLE. THE SHAPE OF THE UPPER TROUGH IN THE 00Z GFS/ECMWF/UKMET BEST MATCHES THE ENSEMBLE MEANS AT THIS POINT...SO A COMPROMISE OF THE THREE MODELS IS PREFERRED. UPPER TROUGH MOVING THROUGH THE EASTERN U.S. TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO