MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1252 AM EDT SAT APR 08 2017 VALID APR 08/0000 UTC THRU APR 11/1200 UTC VALID APR 07/1200 UTC THRU APR 11/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION ALONG WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NO SIGNIFICANT NAM/GFS INITIALIZATION ERRORS WERE NOTED IN AND NEAR NORTH AMERICA. ...DEEP CYCLONE DEPARTING NEW ENGLAND TODAY... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS FEATURE. ...UPPER TROUGH MOVING INTO THE WEST TODAY AND REACHING THE PLAINS BY LATE SUN... ...SURFACE LOW TRACKING THROUGH THE UPPER MS VALLEY SUN NIGHT WITH TRAILING COLD FRONT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND...EXCLUDING THE NAM SURFACE SOLUTION DURING THE FIRST 24 HOURS CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 00Z NAM IS EARLY TO SHOW DIFFERENCES AT 500 MB...WITH A STRONGER/SLOWER VORTICITY MAX OVER NRN NEVADA AT F024 HRS...00Z/09...COMPARED TO THE REMAINING DETERMINISTIC AND ENSEMBLE MAJORITY INDICATING THIS FEATURE ALONG THE UT/NV BORDER. HOWEVER...THE IMPACTS ON THIS ANOMALY IN THE NAM DO NOT APPEAR TO BE SIGNIFICANT FOR THE REMAINDER OF THE FORECAST. THE 00Z GFS DOES NOT SHOW LIKE THE NAM ACROSS NV BUT APPEARS TO BE TOWARD THE FASTER END OF THE LATEST GUIDANCE BY 00Z/10 WHILE OTHER MODELS AND ENSEMBLE SPAGHETTI HEIGHTS ARE SHOWING SLOWER TRENDS. THESE TRENDS MAKE SENSE GIVEN THE ANOMALOUS MID-LEVEL RIDGE LOCATED DOWNSTREAM. BY 00Z/10...THE LATEST SPAGHETTI HEIGHT PLOTS SHOW THE 12Z ECMWF/UKMET TOWARD THE WEAKER SIDE WITH THE 552 DM HEIGHT...MORE SO IN THE 12Z UKMET...AND THE 12Z CMC BEGINS TO SHOW AS A SLOW OUTLIER. IN AN ATTEMPT TO STAY CLOSER TO THE 12Z ECMWF MEAN OR 18Z GEFS MEAN...WHICH ARE BETWEEN THE 00Z GFS AND 12Z ECMWF...THE BEST DETERMINISTIC BLEND THAT REPRESENTS THE PREFERRED SOLUTION IS A BLEND OF THE 00Z NAM AND 12Z ECMWF. ...UPPER TROUGH/SURFACE COLD FRONT REACHING THE PACIFIC NORTHWEST LATE SUN/SUN NIGHT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/NAM COMPROMISE CONFIDENCE: AVERAGE THE MODELS ARE STRUGGLING WITH HOW TO HANDLE ENERGY IN THE BASE OF AN UPPER TROUGH APPROACHING THE PACIFIC NORTHWEST ON SUN...AND TRACKING IT UNDER A MID-LEVEL RIDGE IN WRN CANADA. THE 12Z ECMWF SHOWS DIFFERENTLY WITH HOLDING THE CORE OF A POTENT VORTICITY MAX WITHIN THE TROUGH FARTHER NORTH MON MORNING...WHICH IMPACTS THE SHAPE OF THE DOWNSTREAM TROUGH EVOLUTION. BY 00Z-12Z/11...THE 12Z ECMWF IS FARTHER NORTH WITH THIS FEATURE...WHILE THE 00Z NAM/GFS SHOW BETTER AGREEMENT TO EACH OTHER AND THE LATEST ENSEMBLE MEAN GUIDANCE. THE 12Z UKMET/CMC DO NOT AGREE WITH THE ENSEMBLE SPAGHETTI CLUSTERING AND ARE DISCOUNTED AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO