MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1217 AM EST MON JAN 02 2017 VALID JAN 02/0000 UTC THRU JAN 05/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... ...NEGATIVELY-TILTED TROUGH EXITING INTO THE CANADIAN MARITIMES... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: HIGH WITHIN A REGION OF BROAD CYCLONIC FLOW EXTENDING ACROSS CENTRAL/EASTERN CANADA WILL FEATURE AN EMBEDDED SHORTWAVE LIFTING TOWARD NEWFOUNDLAND. GIVEN THE SYSTEM IS NO LONGER OF CONSEQUENCE OF THE STATES...A GENERAL MODEL COMPROMISE IS SUGGESTED. ...SHEARING SHORTWAVE CURRENTLY CROSSING THE MIDDLE MS VALLEY... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: HIGH WITHIN A REGION OF MID-LEVEL SOUTHWESTERLY FLOW...A SHEARING SHORTWAVE WAS SEEN LIFTING OUT OF THE CENTRAL PLAINS. RADAR IMAGERY SHOWED A BAND OF LIGHT TO LOCALLY MODERATE SNOW AFFECTING THE DAKOTAS INTO THE UPPER MIDWEST. MODELS AGREE ON CONTINUED SHEARING AS THE SYSTEM FEELS THE INFLUENCE OF A DOWNSTREAM RIDGE. A GENERAL MODEL COMPROMISE IS WARRANTED GIVEN SUFFICIENT MODEL AGREEMENT. ...POTENT SHORTWAVE EJECTING OUT OF NORTH-CENTRAL MX TOWARD THE ARKLATEX... ...EVENTUAL STRONG COASTAL LOW MOVING UP THE EASTERN SEABOARD... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: AVERAGE FORMERLY A CLOSED LOW MOVING OUT OF THE SOUTHERN CA...A PROGRESSIVE SHORTWAVE CURRENTLY JUST WEST OF EL PASO TX WILL CONTINUE TO ACCELERATE NORTH OF EAST THE NEXT COUPLE OF DAYS. JUST LIKE YESTERDAY...THE 12Z UKMET IS TO THE SOUTH OF THE CONSENSUS AS THE WAVE MOVES THROUGH THE SOUTHERN/SOUTHEASTERN U.S. LIKE PRECEDING SYSTEMS...THE SHORTWAVE ENERGY WILL LIFT NORTHWARD ALONG THE EASTERN SEABOARD WITH DECENT DEEPENING OCCURRING. CONSIDERING THE SURFACE LOW PLACEMENT AMONG THE ENSEMBLE CAMPS...THE CMC ENSEMBLES HAVE BEEN QUICKER WHILE THE GEFS/ECMWF MEMBERS ARE ABOUT 6 HOURS OR SO BEHIND. THE MOST STABLE AMONG THE BUNCH HAS BEEN THE ECMWF SOLUTIONS AS THEY HAVE BEEN IN A SIMILAR LOCATION THE PAST FOUR RUNS DATING BACK TO THE 31/0000Z MODEL CYCLE. THE GEFS HAVE FINALLY CAUGHT ON AFTER OVEREMPHASIZING THE NORTHERN STREAM LOW FOR MULTIPLE CYCLES IN A ROW. WILL LEAN ON THIS ECMWF SUITE STABILITY AND FAVOR A COMBINATION OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN HERE. ...SYSTEM SLIPPING OUT OF THE NORTHERN ROCKIES TOWARD THE GREAT LAKES THE NEXT TWO DAYS... ...ASSOCIATED WEAK AREA OF LOW PRESSURE... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF WITH THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: AVERAGE RECENT WATER VAPOR IMAGERY SHOWED A VERY HIGH AMPLITUDE AND BLOCKED PATTERN ACROSS THE EASTERN PACIFIC INTO THE WESTERN U.S. A PERSISTENT/SEMI-PERMANENT UPPER HIGH CONTINUES TO DOMINATE THE GULF OF AK WHILE CLOSED LOWS ARE FEATURED UNDERNEATH. A SPLIT IS CURRENTLY UNDERWAY ACROSS THE PACIFIC NORTHWEST/UPPER INTERMOUNTAIN WEST WITH A SHORTWAVE CURRENTLY DRIFTING AWAY FROM THE OR/ID BORDER. ONE OF THE BIGGER TRENDS NOTED IS THE FACT THE GFS HAS REALLY BACKED OFF ON THE DEEP SURFACE LOW SEEN FROM SOME OF THE PREVIOUS DAYS. LOOKING AT THE CURRENT GUIDANCE...THE 00Z GFS HAS MADE A MOVE IN THE QUICKER DIRECTION RELATIVE TO THE CLUSTERED ENSEMBLE MEANS. GIVEN THE SOLUTIONS HAVE GENERALLY BEEN MAKING A MOVE TOWARD THE ECMWF WHICH HAS NOT REALLY BUDGED IN RECENT DAYS...WILL LEAN MORE HEAVILY ON ITS OUTPUT. GIVEN SOME SPREAD...WILL INCORPORATE THE 18Z GEFS/12Z ECMWF ENSEMBLE MEAN INTO THE MIX WITH THE 12Z ECMWF. ...UPPER LOW SETTING UP IN THE VICINITY OF THE PACIFIC NORTHWEST THROUGH MID-WEEK... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF WITH THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE WITHIN THE AFOREMENTIONED LONGWAVE TROUGH ACROSS THE PACIFIC NORTHWEST...A CLOSED LOW WILL PEEL OFF AND MEANDER BACK TOWARD THE EASTERN PACIFIC. BY 04/0000Z...THERE IS QUITE A BIT OF SPREAD BUILDING AS SOME OF THE SOLUTIONS CARRY THE UPPER SYSTEM WEST OF 130W LONGITUDE. THE 00Z NAM/12Z UKMET HAVE GENERALLY BEEN NORTH AND WEST OF THE CONSENSUS AND HAVE CONTINUED THAT HERE. THE 12Z CMC AND SOME OF ITS PREVIOUS RUNS HAVE BEEN QUITE A BIT MORE ROBUST WITH THE STRENGTH OF THE MID-LEVEL CENTER. ENSEMBLE SPAGHETTI PLOTS HAVE BEEN CONSISTENT WITH A CLOSED LOW CENTER JUST OFFSHORE OF OREGON ON WEDNESDAY MORNING. THE 12Z ECMWF HAS REMAINED WITHIN THIS ENSEMBLE CAMP BASED ON EVALUATION OF RECENT SPAGHETTI PLOTS. GIVEN THE VAST SPREAD...WILL SPLIT THE DIFFERENCE BETWEEN THE 12Z ECMWF AND THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS ...POSITIVELY-TILTED TROUGH SINKING THROUGH THE NORTHERN HIGH PLAINS BY 05/0000Z... PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: BELOW AVERAGE TOWARD THE END OF THE PERIOD...THERE ARE A SERIES OF DIFFERENCES WITH A POSITIVELY-TILTED TROUGH SLIDING THROUGH THE NORTHERN HIGH PLAINS AND EVENTUALLY PROJECTING DOWNSTREAM TOWARD THE MO VALLEY. THERE IS A LOT OF DISAGREEMENT IN HOW QUICKLY THIS WILL TAKE PLACE WITH THE FASTER CAMP CONTAINING THE 00Z NAM/GFS AS WELL AS THE 12Z UKMET. ON THE MUCH SLOWER SIDE ARE THE 12Z ECMWF/CMC. ENSEMBLE MEANS APPEAR TO MIMIC THEIR DETERMINISTIC COUNTERPARTS. GIVEN THIS ASSESSMENT...AN EVEN SPLIT OF THE MEANS IS RECOMMENDED UNTIL THE MODELS MOVE INTO BETTER AGREEMENT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER