MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1250 AM EDT MON APR 10 2017 VALID APR 10/0000 UTC THRU APR 13/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NO SIGNIFICANT NAM/GFS INITIALIZATION ERRORS WERE NOTED IN AND NEAR NORTH AMERICA. ...UPPER TROUGH REACHING THE UPPER MS VALLEY TONIGHT... ...NEGATIVELY TILTED OVER NEW ENGLAND WED NIGHT... ...SURFACE LOW TRACKING THROUGH THE GREAT LAKES TONIGHT AND TUESDAY WITH TRAILING COLD FRONT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/00Z GFS/12Z ECMWF BLEND CONFIDENCE: AVERAGE THERE CONTINUE TO BE SOME ADJUSTMENTS MADE WITH THE TIMING OF THE UPPER TROUGH CROSSING THE GREAT LAKES REGION ON TUE BUT THE ECMWF MEAN HAS BEEN CONSISTENT FROM RUN TO RUN AND MOST MODELS AGREE WITH THE 500 MB TROUGH TIMING ALTHOUGH THE 00Z GFS MAY BE A BIT FASTER THAN MOST. REGARDING THE SURFACE LOW...THE 12Z UKMET IS THE ODD MAN OUT WITH ITS SURFACE LOW TRACK TO THE WEST. ENSEMBLES SUPPORT A BLEND OF THE 00Z NAM/GFS AND 12Z ECMWF WITH THE SURFACE LOW TRACK AND UPPER TROUGH THROUGH THE GREAT LAKES REGION ALONG WITH A REINFORCING UPPER TROUGH WHICH ACQUIRES A NEGATIVE TILT OVER THE NORTHEAST WED NIGHT. ...UPPER TROUGH/SURFACE COLD FRONT CROSSING THE INTERIOR NORTHWEST TODAY... ...REMNANT ENERGY ALONG THE CNTRL U.S./CANADIAN BORDER THROUGH WED MORNING... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. ...SHORTWAVE TROUGH/SURFACE LOW APPROACHING THE NORTHWEST COAST LATE TUE/EARLY WED... ...DEEP UPSTREAM LOW APPROACHING THE WEST COAST LATE WED... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 12Z ECMWF IS CLOSEST TO THE ENSEMBLE MEANS REGARDING TIMING AND STRENGTH OF THE SURFACE LOW APPROACHING THE WEST COAST LATE TUE/EARLY WED AND THE 500 MB LOW. THE 00Z NAM AND 00Z GFS ARE FASTER WITH THE LOW TRACK AND ARE ALSO WEAKER THAN THE LATEST GEFS/ECMWF MEANS. THE ENSEMBLES HAVE BEEN TRENDING QUICKER BUT THE 00Z NAM/GFS ARE ON THE FASTER SIDE OF THE LOW SPREAD AT THE MOMENT. GIVEN THE COMPLEX INTERACTION THAT IS DRIVING THE UPPER PATTERN OFF OF THE WEST COAST...STAYING TOWARD THE MIDDLE OF THE ENSEMBLES AT THIS TIME IS RECOMMENDED. ...PACIFIC MID-UPPER LEVEL SHORTWAVE REACHING THE NORTHERN/CENTRAL PLAINS ON WED... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/GFS..12Z CMC BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE ENSEMBLE SPAGHETTI HEIGHTS HAVE SHOWN A SHIFT TOWARD A SHIFT WITH THE 12Z/09 CYCLE TO INDICATE A STRONGER SHORTWAVE TO REACH THE CNTRL/NRN PLAINS ON WED. THE UPSTREAM ENERGY REACHES THE WEST COAST EARLY ON TUE AND IS RATHER ELONGATED FROM NORTH TO SOUTH...WITH MODELS DIFFERING WITH HOW THIS ENERGY EVOLVES DOWNSTREAM. THE 12Z UKMET IS ON BOARD WITH THE IDEA OF A STRONGER SHORTWAVE AS WELL AS THE 00Z NAM AND 12Z CMC TO SOME EXTENT. ONLY THE 12Z ECMWF DIFFERS SIGNIFICANTLY WITH MORE UPPER LEVEL SHORTWAVE ENERGY TRACKING THROUGH THE FOUR CORNERS REGION WHILE THE REMAINING DETERMINISTIC CONSENSUS IS FARTHER NORTH AND MORE POTENT. GIVEN THERE IS NOT YET STRONG SUPPORT FROM THE ECMWF/CMC ENSEMBLES FOR A STRONGER SHORTWAVE...CONFIDENCE IS LOWER THAN AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO