MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 157 AM EST WED JAN 4 2017 VALID JAN 4/0000 UTC THRU JAN 7/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z FINAL MODEL EVALUATION ALONG WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ STORM SYSTEM EXITING THE NORTHEAST U.S. ON WEDNESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE SOUTHERN-STREAM SHORTWAVE TRACKING NORTHEASTWARD ACROSS NEW ENGLAND TUESDAY NIGHT INTO WEDNESDAY WILL LIFT NORTHWARD INTO CANADA. THE INTENSIFYING SURFACE LOW WILL ALSO CONTINUE LIFTING NORTHWARD THE EASTERN CANADIAN PROVINCES AND MERGE WITH THE LOW TO ITS WEST. THE MODELS HAVE COME INTO BETTER AGREEMENT WITH THIS SYSTEM, AND THE 00 CMC TRENDED CLOSER TO THE MODEL CONSENSUS WITH THE AMPLITUDE OF THE TROUGH. THEREFORE, A GENERAL MODEL COMPROMISE CAN BE RECOMMENDED. CLOSED LOW DEVELOPING OVER THE UPPER GREAT LAKES AND CANADA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE A NORTHERN STREAM SHORTWAVE TROUGH OVER THE WESTERN GREAT LAKES AT THE BEGINNING OF THE PERIOD IS PROGGED TO EVOLVE INTO A CLOSED MID-LEVEL LOW OVER EASTERN ONTARIO AND QUEBEC BY WEDNESDAY NIGHT AND DEEPEN SIGNIFICANTLY. THIS WILL SERVE TO STRENGTHEN THE SURFACE LOW OVER QUEBEC BY THURSDAY MORNING THAT JOINS FORCES WITH THE NEW ENGLAND LOW DESCRIBED IN THE PREVIOUS SECTION. GOOD OVERALL MODEL AGREEMENT NOW EXISTS WITH THE HANDLING OF THE UPPER LOW AND ITS ASSOCIATED HEIGHT PATTERN, AND THEREFORE A GENERAL MODEL COMPROMISE CAN BE USED FOR THIS SYSTEM. SECONDARY TROUGH SETTING UP ACROSS THE NORTH-CENTRAL U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z EC MEAN CONFIDENCE: NEAR AVERAGE BY WEDNESDAY MORNING, A SECONDARY TROUGH AND SHORTWAVE IMPULSE DIVING SOUTHWARD FROM CENTRAL CANADA SHOULD REACH THE NORTHERN PLAINS AND THEN THE UPPER MIDWEST BY THURSDAY MORNING. THIS WILL HELP TO REINFORCE THE LARGE SCALE TROUGH OVER THE NORTH-CENTRAL U.S. AND INTO CANADA FOR THE END OF THE WEEK, WITH A SHEARED LOBE OF VORTICITY ACCOMPANYING THIS TROUGH. THE GFS AND THE GEFS MEAN CONTINUE TO SHOW THE LEAST AMOUNT OF AMPLIFICATION WITH THIS TROUGH, AND THE 00Z CMC HAS TRENDED CLOSER TO THE MODEL CONSENSUS COMPARED TO ITS EARLIER RUN. THE NAM IS SLIGHTLY MORE AMPLIFIED TOWARDS THE END OF THE PERIOD. THE EC MEAN IS STILL THE CLOSEST TO THE MODEL CONSENSUS AND THUS CAN BE RECOMMENDED FOR NOW. PACIFIC NORTHWEST TROUGH TRACKING TO THE SOUTHERN PLAINS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/00Z GFS/12Z EC MEAN CONFIDENCE: NEAR AVERAGE A MID-LEVEL TROUGH ORIENTED ROUGHLY WEST TO EAST ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES IS FORECAST TO REMAIN QUASI-STATIONARY THROUGH THURSDAY MORNING. IT SHOULD THEN PROGRESS SOUTHEASTWARD ACROSS THE ROCKIES AND REACH THE SOUTHERN PLAINS BY THE END OF THE FORECAST PERIOD. SHORTWAVE ENERGY WITH THE TROUGH WILL ALLOW FOR THE WESTERN PORTION TO EVOLVE INTO A CLOSED LOW OVER WASHINGTON AND OREGON BEFORE TRANSITIONING BACK INTO AN OPEN WAVE ALOFT. A SURFACE LOW WILL TRACK ACROSS THE INTERMOUNTAIN WEST ALONG A STRONG FRONTAL BOUNDARY, WITH AN ARCTIC AIRMASS TO THE NORTH. ALL OF THE MODEL GUIDANCE INDICATE A TEMPORARY CLOSED LOW OVER WESTERN OREGON ON WEDNESDAY BEFORE EVOLVING INTO AN OPEN WAVE ALOFT. THE CMC IS QUICKEST TO PHASE THIS SHORTWAVE WITH THE TROUGH DIGGING SOUTHWARD ACROSS THE WESTERN HIGH PLAINS WEDNESDAY NIGHT, AND LESS AMPLIFIED WITH THE MID-LEVEL TROUGH. THE OPERATIONAL ECMWF HAS TRENDED MORE AMPLIFIED AND SLOWER AS THE SYSTEM CROSSES THE ROCKIES AND THEN THE SOUTHERN PLAINS, WITH LIMITED SUPPORT FROM THE EC MEAN. THE UKMET IS ALSO ONE OF THE SLOWER SOLUTIONS. SHORTWAVE REACHING THE NORTHERN GREAT LAKES SATURDAY MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE SOME VORTICITY SINKING SOUTH ACROSS CENTRAL CANADA FROM THE POLAR VORTEX ON THE BACK SIDE OF THE LARGE SCALE TROUGH WILL LIKELY SUPPORT A CLOSED LOW NEAR THE NORTHERN GREAT LAKES BY THE END OF THE FORECAST PERIOD SATURDAY MORNING. A REINFORCING COLD FRONT CAN BE EXPECTED ACROSS THE UPPER MIDWEST ALONG WITH THE HEIGHT FALLS FROM THIS LOW. THE 00Z UKMET STILL APPEARS TO BE LESS AMPLIFIED THAN THE OTHER MODEL SOLUTIONS AND SHOWS A TROUGH INSTEAD OF A CLOSED MID-LEVEL LOW. THE CMC BRINGS THE HEIGHT FALLS THE QUICKEST,. THE 00Z NAM, GFS, AND ECMWF ARE IN PRETTY GOOD AGREEMENT AND ALSO SUPPORTED BY THE EC MEAN, MAKING THEM USEFUL COMPONENTS OF THE FORECAST PROCESS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... Hamrick