EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 148 AM EST WED NOV 08 2017 VALID 12Z SAT NOV 11 2017 - 12Z WED NOV 15 2017 ...PATTERN OVERVIEW/MODEL EVALUATION/UNCERTAINTIES/PREFERENCES... WHILE A BROAD UPPER HIGH REMAINS A FIXTURE IN THE FORECAST ACROSS MX AND AT TIMES EXTENDING TOWARD THE RIO GRANDE RIVER VALLEY...AN ACTIVE MID-LATITUDE PATTERN IS EXPECTED TO THE NORTH. A CONVEYOR BELT OF FEATURES WILL TRANSLATE EASTWARD WITH ONE POWERFUL UPPER LOW EXITING TOWARD THE HIGHER LATITUDES OF EASTERN CANADA ON SATURDAY MORNING. ON ITS HEELS...A STRONG SURFACE ANTICYCLONE WILL INHABIT MUCH OF THE EASTERN SEABOARD BRINGING WELL BELOW NORMAL TEMPERATURES TO THE REGION. ACROSS THE GREAT PLAINS...A PACIFIC SHORTWAVE SHOULD BE TRACKING EASTWARD WHILE SOME POTENTIAL PHASING IS NOTED WITH A WAVE MOVING THROUGH SOUTHERN MANITOBA. DEPENDING ON HOW AMPLIFIED THIS SHORTWAVE BECOMES...SOME CYCLOGENESIS WILL LIKELY TAKE PLACE EARLY MONDAY OVER COASTAL NEW ENGLAND BEFORE THE CYCLONE PUSHES OUT TO SEA. LOOKING TO NEXT WEEK...BROAD LONGWAVE RIDGING SHOULD EXTEND FROM THE INTERMOUNTAIN WEST TO THE MS RIVER VALLEY WHILE HEIGHTS BEGIN TO LOWER ALONG THE WEST COAST. A PAIR OF UPPER TROUGHS ARE FORECAST TO SWING THROUGH NORTHERN CA/PACIFIC NORTHWEST...EACH KEEPING CONDITIONS QUITE WET OVER THE REGION. THE LEAD SYSTEM IS FORECAST TO ACCELERATE TOWARD THE GREAT PLAINS LATE TUESDAY WITH THE STRONGER FORCING LIKELY STAYING NORTH OF THE INTERNATIONAL BORDER WITH CANADA. RENEWED HEIGHT FALLS WILL BE PUSHING INTO THE PACIFIC NORTHWEST BY DAY 7/NOVEMBER 15 AS THE PATTERN SEEMS TO BE RATHER LOCKED IN PLACE. MODELS STILL CONTINUE TO STRUGGLE WITH WHETHER TO SHOW A MORE PHASED SOLUTION EVOLVING THROUGH THE CENTRAL U.S. ON SATURDAY. WHILE THE RECENT RUNS OF THE GFS HAVE BEEN ON THE QUICKER SIDE...THE 00Z RUN ARRIVED WITH A MUCH SLOWER SOLUTION WHICH IS EVEN WEST OF THE 12Z ECMWF. THIS 00Z GFS IS ALSO A BIT MORE SUBTLE WITH THE AMPLIFICATION PROCESS WHICH LEADS TO A MORE MODEST WAVE OF LOW PRESSURE. THE 18Z GFS/12Z ECMWF WERE STRONGER THAN THE REMAINING SOLUTIONS AS THE 00Z/12Z CMC/UKMET CARRY A MUCH FLATTER WAVE. EVENTUALLY THE SYSTEM WILL REACH THE EASTERN SEABOARD BY LATE SUNDAY/EARLY MONDAY INDUCING AN AREA OF LOW PRESSURE OFF THE COAST. MOST MODELS ARE MORE SUBTLE WITH THIS DEVELOPMENT ALTHOUGH THE 00Z CMC HAS MOVED TOWARD A MORE EXTREME SOLUTION AS A RAPIDLY STRENGTHENING COASTAL STORM TAKES SHAPE ON TUESDAY OFF THE UPPER MID-ATLANTIC COAST. TURNING THE FOCUS TOWARD THE ACTIVE PACIFIC STORM TRACK...THE LEAD UPPER TROUGH HAS BEEN WELL ADVERTISED FOR THE PAST SEVERAL DAYS. SHORT-TERM ENSEMBLE TRENDS SHOW A SLOWING WHICH THE 00Z UKMET HAS FOLLOWED AFTER ITS FORMER SOLUTION WAS A PROGRESSIVE OUTLIER. BY 14/0000Z...THE 00Z GFS/CMC/UKMET ARE IN REMARKABLY CLOSER AGREEMENT WITH HEIGHT FALLS MOVING INTO EASTERN WA/OR WHILE THE 12Z ECMWF IS A HAIR QUICKER. THE DIFFERENCES EVEN OUT TO DAY 7/NOVEMBER 15 ARE NOT TERRIBLY LARGE WHICH SUGGESTS SLIGHTLY ABOVE AVERAGE FORECAST CONFIDENCE. ON THE HEELS OF THIS LEAD SYSTEM...STRONG HEIGHT FALLS LOOM OFFSHORE WITH ENSEMBLE MEANS IN SOLID AGREEMENT WITH ONE ANOTHER. SOME RUN-TO-RUN CHANGES WERE NOTED IN THE GUIDANCE...PARTICULARLY THE CMC. HOWEVER...ENSEMBLE SPAGHETTI PLOTS DO NOT SHOW A TREMENDOUS AMOUNT OF SPREAD. GIVEN A DECENT SIGNAL OF ALL RELEVANT SOLUTIONS DURING THE PERIOD...WAS ABLE TO KEEP A GOOD CHUNK OF OPERATIONAL GUIDANCE IN THE MIX THROUGHOUT. DID NOT INTRODUCE ANY ENSEMBLE MEANS UNTIL MONDAY WHILE DEDICATING SLIGHTLY MORE WEIGHTING TOWARD THE 12Z ECMWF/ECMWF ENSEMBLE MEAN...60 PERCENT...RELATIVE TO THE 18Z GFS/GEFS MEAN. MAINTAINED THIS RATIO FOR THE ENTIRE PERIOD WITH THE 12Z ECMWF/ECMWF ENSEMBLE MEAN GIVEN A TAD MORE WEIGHT GIVEN ITS STRONGER CONSISTENCY THE PAST FEW DAYS. ...SENSIBLE WEATHER HIGHLIGHTS/THREATS... EXCEPT FOR SATURDAY WHICH WILL BE DOMINATED BY BELOW AVERAGE TEMPERATURES...THE HEAVY INFLUENCE OF PACIFIC AIR MASSES SHOULD CONTRIBUTE TO READINGS CLOSER TO CLIMATOLOGY OR ABOVE IN SOME CASES. BEGINNING IN THE EASTERN THIRD OF THE COUNTRY...STRONG SURFACE RIDGING WILL ALLOW FOR ADEQUATE RADIATIONAL COOLING ON SATURDAY MORNING. THIS WILL BRING THE FIRST FREEZE TO MANY LOCATIONS AS SUCH TEMPERATURES PUSH AS FAR SOUTH AS NASHVILLE TN INTO THE INTERIOR CAROLINAS. WHILE NO DAILY TEMPERATURE RECORDS ARE EXPECTED TO BE BROKEN...SOME RECORD LOWS ARE POSSIBLE OVER THE UPPER GREAT LAKES INTO THE UPPER MID-ATLANTIC/LOWER NEW ENGLAND. LOOKING TO AN AREA WHERE ABOVE NORMAL TEMPERATURES WILL BE THE NORM...GENERAL WESTERLY FLOW SHOULD KEEP CONDITIONS MILD FROM THE ROCKIES EASTWARD TO THE GREAT PLAINS. AT TIMES READINGS 5 TO 10 DEGREES ABOVE CLIMATOLOGY WILL BE WIDESPREAD BY EARLY NEXT WEEK. ACROSS THE PACIFIC NORTHWEST AND INTO NORTHERN CA...AN ACTIVE STORM TRACK SHOULD KEEP CONDITIONS COOL GIVEN THE EXPECTATIONS OF ABUNDANT CLOUDS AND BANDS OF PRECIPITATION. WARM ADVECTION PRECIPITATION ALONG THE ADVANCING FRONT IS IN THE FORECAST FROM THE ARKLATEX UP TO THE GREAT LAKES. GIVEN STRONGER FORCING TO THE NORTH...LOCALLY HEAVIER PRECIPITATION IS POSSIBLE OVER THE GREAT LAKES THIS WEEKEND WITH A THREAT FOR SNOW GIVEN SOME REMNANT ARCTIC AIR REMAINING IN PLACE. THE CHANCES FOR SNOW WILL MOVE TOWARD INTERIOR NEW ENGLAND BY LATE IN THE WEEKEND INTO EARLY NEXT WEEK. AS THE COASTAL LOW DEVELOPS...ANY CLOSER TO TRAJECTORY TO THE COAST WOULD BRING HIGHER AMOUNTS NEAR FAR EASTERN SECTIONS OF THE MID-ATLANTIC/NEW ENGLAND. THE MOST CONSISTENT AREA OF UNSETTLED WEATHER WILL BE ACROSS NORTHERN CA/PACIFIC NORTHWEST INTO THE UPPER INTERMOUNTAIN WEST WITH COASTAL RAIN AND HIGHER ELEVATION SNOWS. THIS MULTI-DAY EVENT SHOULD PERSIST INTO THE MIDDLE OF NEXT WEEK WHICH MAINTAINS THE FAIRLY WET PATTERN. EVENTUALLY A RETURN OF ADDITIONAL SHOWERS ARE POSSIBLE OVER THE MIDDLE MS VALLEY/UPPER MIDWEST/GREAT LAKES BY MID-WEEK AS THE LEAD PACIFIC TROUGH TRACKS EASTWARD. RUBIN-OSTER