MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 150 PM EST FRI DEC 09 2016 VALID DEC 09/1200 UTC THRU DEC 13/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION ALONG WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ LOW AMPLITUDE SHORTWAVE CROSSING THE GREAT LAKES AND NEW ENGLAND THROUGH SATURDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. PROGRESSIVE SHORTWAVE CROSSING THE NRN ROCKIES SAT AND PASSING OVER THE GREAT LAKES EARLY MON WITH ACCOMPANYING SURFACE LOW/FRONT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE MODEST SPREAD REMAINS IN THE LATEST SPAGHETTI ENSEMBLE HEIGHTS FOR SUN NIGHT INTO MON...BUT BETTER AGREEMENT EXISTS COMPARED TO PREVIOUS CYCLES. GIVEN RATHER LARGE ADJUSTMENTS BETWEEN ENSEMBLE CYCLES....CONFIDENCE IS LOWER THAN USUAL. DESPITE LOWER CONFIDENCE OVERALL...THE 12Z UKMET/CMC STAND OUT TOWARD THE FLATTER EDGES OF THE LATEST ENSEMBLE PLOTS...WITH BETTER AGREEMENT TOWARD THE 12Z GFS AND 00Z ECMWF. THE 12Z GFS IS TOWARD THE STRONGER SIDE OF THE DETERMINISTIC MODELS AT 500 MB AND THE NAM IS SOMEWHAT SIMILAR TO THE 12Z GFS/00Z ECMWF AT 500 MB BUT IS ON THE STRONGER SIDE AT 850 MB WITH GREATER AND MORE NORTHWARD DISPLACED LOW LEVEL WARM ADVECTION INTO THE GREAT LAKES. THE ENSEMBLE CONSENSUS HAS NOT BEEN CONSISTENT FROM RUN TO RUN...BUT CURRENT CLUSTERING SUPPORTS PLACEMENT NEAR THE 12Z GFS JUST A BIT FLATTER AND FASTER. AS THE UPPER SYSTEM APPROACHES THE NORTHEAST ON MON...THE GFS/ECMWF CONTINUE TO BE REPRESENTATIVE OF A GOOD COMPROMISE BUT THEY DIFFER ON THE PARENT SURFACE LOW POSITION OVER SRN ONTARIO/QUEBEC. THE ENSEMBLES CURRENTLY SUPPORT THE 12Z GFS OVER THE 00Z/12Z ECMWF WITH THE SURFACE POSITION OVER SRN QUEBEC AND REGARDING THE SURFACE LOW NEAR THE GULF OF MAINE BY 00Z/13. CONTINUED ONSHORE FLOW INTO THE PACIFIC NORTHWEST FROM SUN-MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE FAST MOVING PACIFIC SYSTEMS IN A QUASI-ZONAL FLOW LOCATED JUST OFF OF THE WEST COAST MAKE FOR A DIFFICULT FORECAST. AFTER THE DEPARTURE OF THE SHORTWAVE REFERENCED ABOVE...CONTINUED ONSHORE FLOW INTO THE PACIFIC NORTHWEST REMAINS WITH/AHEAD OF A POSSIBLE CLOSED LOW WEST OF WASHINGTON BY MON. A BLEND OF THE 12Z GFS AND 00Z ECMWF REPRESENT THE MIDDLE OF THE SPREAD WITH THE 12Z ECMWF SWITCHING AWAY FROM THE BETTER ENSEMBLE CLUSTERING WITH THE DEPICTION OF A CLOSED LOW ON THE WRN EDGE OF THE LATEST ENSEMBLE SPAGHETTI HEIGHTS BY MON MORNING. THE 00Z ECMWF WAS IN A MORE PREFERABLE PLACE COMPARED TO THE 12Z ECMWF. THE 12Z UKMET COULD BE CONSIDERED A SECOND CHOICE AS IT IS THE NEXT CLOSEST TO THE PREFERRED POSITION WITH THE POSSIBLE CLOSED LOW BY LATE MON. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO