EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 PM EDT TUE SEP 27 2016 VALID 12Z FRI SEP 30 2016 - 12Z TUE OCT 04 2016 ...GUIDANCE/UNCERTAINTY ASSESSMENT AND PATTERN HIGHLIGHTS/THREATS.... A WET UPPER LEVEL CLOSED/CUTOFF LOW WILL VERY SLOWLY LIFT OUT OF THE OHIO VALLEY THROUGH THE WEEKEND WHILE TROUGHING IS REINFORCED INTO THE UNSETTLED WRN US. THE MIDDLE SECTION OF THE COUNTRY WILL START DRY AND MILD BUT WILL SEE AN INCREASED CHANCE OF RAIN LATE WEEKEND INTO EARLY NEXT WEEK. MEANWHILE...THE POTENTIAL FOR SHORT TERM TROPICAL LOW DEVELOPMENT ACROSS THE CARRIBEAN MAY LEAD TO A THREAT FOR THE SERN US EARLY NEXT WEEK. THIS IS BEING MONITORED BY THE NHC AND WPC. MODELS AND ENSEMBLES HAVE INCREASINGLY SETTLED ON A COMMON SOLUTION REGARDING THE EVOLUTION OF AN UPPER/CLOSED LOW IN THE EAST. THERE IS AGREEMENT THAT A CLOSED LOW WILL COMPLETELY CUT OFF FROM THE WESTERLIES NEAR THU/FRI AND THEN SLOWLY LIFT NORTHWARD THIS WEEKEND. A +2 SIGMA HEIGHT ANOMALY NEAR JAMES BAY IS FORECAST TO SLOWLY MOVE NORTHEASTWARD THROUGH THE PERIOD WHICH FAVORS A SLOW EXODUS OF THE CLOSED LOW TO ITS SOUTH THROUGH NEW ENGLAND AROUND MONDAY. THE 00 UTC ECMWF/ECMWF ENSEMBLES REMAIN THE SLOWEST TO MOVE THE CLOSED LOW AWAY FROM THE GREAT LAKES COMPARED TO THE GFS/CANADIAN AND RESPECTIVE ENSEMBLES. PREFER A COMPOSITE 06 UTC GFS...00 UTC ECMWF...AND 00 UTC NAEFS ENSEMBLE BLEND GIVEN THE DISAGREEMENT IN THE WEST AS TO THE ORIENTATION OF THE TROUGH AND UNCERTAINTY IN EMBEDDED SHORTWAVES. WITH THE CLOSED LOW NEARLY STUCK IN THE EAST FOR SEVERAL DAYS...AN INFLUX OF MOISTURE FROM THE ATLANTIC WILL BE CHANNELED INTO THE MID-ATLANTIC AND NORTHEAST IN WAVES. COOLER THAN AVERAGE DAYTIME HIGHS ARE EXPECTED WITH ABUNDANT CLOUDINESS. AS THE UPPER LOW WEAKENS AND FILLS OVER TIM...PRECIPITATION COVERAGE WILL GRADUALLY DECREASE INTO NEXT WEEK. COLD POOL ALOFT SUGGESTS LINGERING CLOUDS AROUND THE DECAYING CIRCULATION WITH AFTERNOON HEATING. THE ENSEMBLES FOCUS THE PRECIPITATION INITIALLY ON THE MID-ATLANTIC LATER THIS WEEK (THU-FRI) AND THEN NORTHWARD INTO THE NORTHEAST AS THE UPPER AND SFC SYSTEMS MOVE NORTHWARD. TAIL END OF THE FRONTAL BOUNDARY WILL LINGER AROUND FLORIDA WHICH WILL KEEP RAIN IN THE FORECAST NEARLY EVERY DAY FOR CENTRAL/SOUTH PORTIONS. THIS COULD BECOME A RENEWED FOCUS FOR TROPICAL MOISTURE EARLY NEXT WEEK WITH POSSIBLE LOW DEVELOPMENT AND APPROACH FROM THE CARIBBEAN AS EFFECTED BY A GENERAL MEAN WEKANESS TO LIFT FEATURES. THE WEST WILL SEE A WAVY LEAD FRONT LINGER INTO FRI AND THEN SLOWLY PROGRESS EASTWARD THIS WEEKEND...BRINGING COOLER TEMPERATURES TO THE N-CENTRAL INTERMOUNTAIN WEST/ROCKIES AND EVENTUALLY INTO THE HIGH PLAINS. MUCH OF THE PACIFIC NORTHWEST INTO NORTHERN/CENTRAL CALIFORNIA AND THE REST OF THE GREAT BASIN WILL SEE BELOW AVERAGE TEMPERATURES AS THE TROUGH GETS REINFORCED THIS WEEKEND INTO NEXT WEEK. PRECIPITATION WILL SPREAD EASTWARD THROUGH THE CENTRAL AND NORTHERN ROCKIES AS THE FRONT MOVES SOUTH AND EAST. THE POTENTIAL EXISTS FOR EVEN MORE ENERGY TO DIG INTO THE BASE OF THE TROUGH WITH MORE SEPARATION THAT MOST GUIDANCE EARLY NEXT WEEK GIVEN RECENT PATTERN TRENDS AND UPSTREAM RIDGE AMPLITUDE. WPC PROGS UTILIZE THE 00 UTC NAEFS BY DAYS 6/7 TO BETTER DEPICT THIS POTENITAL. THIS HOLDS HEIGHTS LOWER THAN THE 00 UTC ECMWF AND 06 UTC GFS BUT NOT AS MUCH AS SHOWN BY THE 00 UTC CANADIAN. SCHICHTEL