MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1245 PM EDT MON OCT 31 2016 VALID OCT 31/1200 UTC THRU NOV 04/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING THE NAM/GFS AND PRELIMINARY MODEL PREFERENCES ...TROUGH MOVING INTO THE WEST COAST TODAY/TONIGHT... ...UPPER LOW CLOSING OFF ACROSS THE SOUTHWESTERN U.S. ON WEDNESDAY... PRELIMINARY PREFERENCE: GFS/00Z ECMWF BLEND CONFIDENCE: AVERAGE THE NAM IS GENERALLY A BIT MORE AMPLIFIED WITH THE TROUGH THROUGH THE SHORT RANGE FORECAST PERIOD. THE NAM ALSO CLOSES OFF THE UPPER LOW A LITTLE FARTHER NORTHEAST ACROSS THE SOUTHWEST RELATIVE TO CONSENSUS. THE GFS AND 00Z ECMWF ARE GENERALLY IN THE MIDDLE OF THE SPREAD WITH RESPECT TO AMPLITUDE OF THE TROUGH AS IT MOVES INLAND -- AND THE GFS CLOSES OFF THE UPPER LOW MUCH CLOSER TO THE LOCATION OF THE 00Z ECMWF, WEST OF THE NAM. GIVEN THE GENERALLY SIMILAR SOLUTIONS, WILL RECOMMEND A BLEND OF THE GFS AND 00Z ECMWF. ...LOW PRESSURE SYSTEM CROSSING THE NORTHERN PLAINS TODAY... ...COLD FRONT ENTERING THE NORTHEAST ON WEDNESDAY... PRELIMINARY PREFERENCE: GFS/00Z ECMWF BLEND CONFIDENCE: AVERAGE THE NAM IS SLOWER THAN CONSENSUS WITH THE PROGRESSION OF THE UPPER-LEVEL SHORTWAVE ACROSS THE NORTHERN PLAINS EVEN EARLY ON IN THE FORECAST. THE GFS IS VERY CLOSE TO THE 00Z ECMWF WITH RESPECT TO THE WAVE TIMING AND AMPLITUDE OF THE WAVE. AT THE SURFACE, THE GFS AND 00Z ECMWF ARE IN GENERALLY GOOD AGREEMENT AS THE LOW CENTER TRACKS NORTHEASTWARD ACROSS NORTHERN MINNESOTA BY THIS EVENING AND THEN INTO ONTARIO AND QUEBEC TONIGHT AND WEDNESDAY. THE SURFACE COLD FRONT IS FORECAST TO REACH THE NORTHEASTERN U.S. ON WEDNESDAY. GIVEN THE GENERAL AGREEMENT BETWEEN THE GFS AND 00Z ECMWF ALOFT AND AT THE SURFACE, WILL RECOMMEND A BLEND OF THESE TWO SOLUTION AT THIS TIME. ...SHORTWAVE CROSSING THE NORTHERN PLAINS ON WEDNESDAY... ...SURFACE LOW DEVELOPING THE GREAT LAKES WEDNESDAY... ...TROUGH AMPLIFYING ACROSS THE EASTERN U.S. ON THURSDAY... PRELIMINARY PREFERENCE: GFS/00Z ECMWF BLEND CONFIDENCE: AVERAGE SHORTWAVE ENERGY IS FORECAST TO MOVE INTO THE NORTHERN ROCKIES/NORTHERN HIGH PLAINS LATE TUESDAY INTO WEDNESDAY. THIS WAVE WILL GRADUALLY AMPLIFY THROUGH THE SHORT RANGE FORECAST PERIOD AS IT MOVES EAST, EVOLVING INTO A RELATIVELY LARGE TROUGH ACROSS THE EASTERN U.S. BY THURSDAY. A FRONTAL BOUNDARY WILL BE LINGERING ACROSS THE OHIO VALLEY/GREAT LAKES AT THIS TIME, AND A WAVE OF LOW PRESSURE IS FORECAST TO DEVELOP ALONG THE FRONT ACROSS THE GREAT LAKES LATE WED OR WED NIGHT. BOTH THE NAM AND GFS HAVE TRENDED SLIGHTLY SLOWER WITH THE EASTWARD PROGRESSION OF THE TROUGH BY THURSDAY AS IT AMPLIFIES ACROSS THE GREAT LAKES/OHIO VALLEY. GIVEN THAT THE 00Z ECMWF APPEARS TO BE SLIGHTLY FASTER THAN THE 00Z ECMWF ENSEMBLE MEAN, AM NOT WILLING TO DISCOUNT THE SLOWER GFS SOLUTION. AT THE SURFACE, DIFFERENCES ARE LESS, WITH THE GFS AND 00Z ECMWF SHOWING A VERY SIMILAR DEVELOPMENT AND PROGRESSION OF THE SURFACE LOW THURSDAY. ...SHORTWAVE AND SURFACE FRONTAL BOUNDARY REACHING THE PACIFIC NORTHWEST ON WEDNESDAY... PRELIMINARY PREFERENCE: GFS/00Z UKMET BLEND CONFIDENCE: AVERAGE THE NAM IS ON THE SLOW END OF THE SPREAD WITH RESPECT TO THE TIMING OF THIS SHORTWAVE AND THE SURFACE FRONT. THE GFS IS VERY SIMILAR TO THE 00Z UKMET, SHOWING A STRONGER SHORTWAVE RELATIVE TO THE 00Z ECMWF, WHICH RESULTS IN A STRONGER (AND SLOWER) SURFACE LOW WEST OF BRITISH COLUMBIA THURSDAY NIGHT. THE GFS SOLUTION HAS NOT CHANGED SIGNIFICANTLY FROM ITS 06Z OR 00Z RUNS, GIVING THIS SOLUTION ADDITIONAL WEIGHT FROM CONSISTENCY. THE ECMWF HAS SHOWN MUCH LARGER RUN-TO-RUN DISCONTINUITIES, WITH THE 12Z RUN FROM YESTERDAY MUCH SIMILAR TO THE RECENT GFS SOLUTIONS AS WELL AS THE 00Z UKMET. THUS, AT THIS TIME WILL LEAN IN THE DIRECTION OF THE GFS/00Z UKMET, SHOWING A SLOWER AND STRONGER SYSTEM AT 00Z FRIDAY WEST OF BRITISH COLUMBIA. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RYAN