MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1156 PM EST THU DEC 8 2016 VALID DEC 9/0000 UTC THRU DEC 12/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS MODEL EVALUATION ALONG WITH PREFERENCES AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ***00Z NAM INITIALIZED 850MB TEMPERATURES 3-4 DEGREES C TOO COLD OVER PARTS OF THE PACIFIC NORTHWEST*** DEEP UPPER TROUGH SWINGING THROUGH THE NORTHEASTERN U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE LARGE SYNOPTIC SCALE TROUGH OVER THE NORTHEAST U.S. AT THE BEGINNING OF THE PERIOD IS PROGGED TO MOVE OVER THE CANADIAN MARITIMES BY FRIDAY. GOOD OVERALL MODEL AGREEMENT EXISTS TO SUPPORT A GENERAL MODEL COMPROMISE HERE. LOW AMPLITUDE SHORTWAVE CROSSING THE GREAT LAKES AND NEW ENGLAND THROUGH SATURDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/12Z UKMET/12Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE A COUPLE OF WEAK SHORTWAVES CURRENTLY OVER SOUTH-CENTRAL CANADA SHOULD MIGRATE EASTWARD AND CONSOLIDATE INTO A LOW-AMPLITUDE LONGWAVE TROUGH WHICH WILL MOVE ACROSS THE GREAT LAKES BY FRIDAY NIGHT AND INTO SATURDAY. THE 12Z CMC IS STILL WEAKER AND SLOWER THAN THE MODEL CONSENSUS, WHILST THE GFS IS MORE AMPLIFIED WITH THE TROUGH. THIS TREND CONTINUES INTO SUNDAY AS THE TROUGH MOVES OVER NEW ENGLAND. PROGRESSIVE SHORTWAVE AND SURFACE LOW REACHING THE MIDWEST BY MONDAY MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z ECMWF/12Z UKMET/12Z CMC CONFIDENCE: SLIGHTLY BELOW AVERAGE A SURFACE LOW TRACKING FROM THE LEE OF THE ROCKIES SATURDAY AFTERNOON TO THE OHIO VALLEY BY MONDAY MORNING WILL BE SUPPORTED BY A BROAD MID-LEVEL TROUGH ORIGINATING FROM THE PACIFIC NORTHWEST. BY THE END OF THE FORECAST PERIOD ON MONDAY, THE CMC/ECMWF/UKMET ARE WELL CLUSTERED OVER INDIANA AND OHIO, AND THE NAM AND GFS FARTHER TO THE NORTH AND STRONGER WITH THE SURFACE LOW. THE NAM IS AN OUTLIER WITH HAVING AN OVER-AMPLIFIED TROUGH OVER THE MIDWEST, AND THE GFS IS MORE PROGRESSIVE THAN THE MODEL CONSENSUS. PACIFIC STORM SYSTEM AFFECTING THE PACIFIC NORTHWEST THIS WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET/18Z GEFS MEAN CONFIDENCE: SLIGHTLY BELOW AVERAGE A STRONG PACIFIC STORM OFF THE PACIFIC NORTHWEST COAST ON FRIDAY IS PROGGED TO APPROACH THIS REGION ON SATURDAY, WITH THE SURFACE LOW EXPECTED TO REACH NORTHWESTERN WASHINGTON AROUND 00Z SUNDAY. THE 12Z ECMWF IS STILL INDICATING TWO SEPARATE LOWS PIVOTING AROUND EACH OTHER THROUGH THE FIRST 36 HOURS OF THE FORECAST, WHEREAS THE OTHER MODELS ARE ON BOARD WITH THE IDEA OF ONE MAIN SURFACE LOW. LOOKING ALOFT, THE NAM BECOMES MORE AMPLIFIED WITH THE SHORTWAVE AXIS BY 36 HOURS, AND THE 12Z EC MEAN IS A BIT SLOWER THAN THE MODEL CONSENSUS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... HAMRICK