EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1059 AM EST THU NOV 24 2016 VALID 12Z SUN NOV 27 2016 - 12Z THU DEC 01 2016 ...OVERVIEW... GUIDANCE IS STABLE IN DEPICTING THE LONGWAVE PATTERN SETTLING INTO AN AMPLIFIED CONUS TROUGH BTWN ERN PAC AND WRN ATLC MEAN RIDGES. FROM SOME COMBINATION OF THE FCST EXTENDING ANOTHER DAY FORWARD IN TIME AND/OR THE ERN PAC RIDGE TRENDING SOMEWHAT STRONGER... CURRENT INDICATIONS ARE THAT THE NRN PAC TROUGH ENERGY REACHING THE WEST LATE IN THE PERIOD MAY HERALD A WWD ADJUSTMENT IN TROUGH EMPHASIS AROUND AND BEYOND THE END OF THE MEDIUM RANGE PERIOD. THE MOST PROMINENT FOCUS IN THE SENSIBLE WEATHER REALM WILL BE ON A BROAD AREA OF ACTIVE WEATHER FROM PARTS OF THE PLAINS INTO THE ERN U.S.. WARM SECTOR HVY RNFL MAY EXTEND INTO DROUGHT AREAS OF THE SOUTH WHILE NRN TIER LOCATIONS MAY SEE SOME SNOW. STRONG WINDS ARE ALSO PSBL. ...GUIDANCE/PREDICTABILITY ASSESSMENT... MODELS/ENSEMBLES ARE STILL SHOWING A FAIR AMOUNT OF DIFFICULTY IN RESOLVING THE SPECIFICS OF MULTIPLE PIECES OF ENERGY ALOFT THAT WILL EMERGE INTO THE PLAINS AND AFFECT IMPORTANT SFC DETAILS. THERE IS DECENT AGREEMENT ON THE CLOSING OF LEADING ENERGY INTO A NRN PLAINS CLOSED LOW BY DAY 4 MON BUT WITH PERSISTENT DIFFS ON STRENGTH/TIMING OF THE SFC LOW. THE MAJORITY OF GUIDANCE SUGGESTS THE LOW WILL BE A LITTLE FASTER/WEAKER THAN THE PAST COUPLE ECMWF RUNS BUT PERHAPS NOT TO THE EXTENT OF THE 06Z GFS/GEFS MEAN. INTERESTINGLY AS OF 12Z TUE THE 00Z GFS/ECMWF HAVE ESSENTIALLY FLIPPED THEIR RELATIVE POSNS IN THE SOLN SPREAD VS 24 HRS AGO... FURTHER SUPPORTING AN INTERMEDIATE SOLN THAT IS FAIRLY CLOSE TO CONTINUITY. A GREATER SOURCE OF UNCERTAINTY IS ENERGY NOW OVER THE ALEUTIANS/BERING SEA AND FCST TO REACH THE WEST COAST BY EARLY DAY 3 SUN. INDIVIDUAL MODEL RUNS HAVE BEEN INCONSISTENT AND VARIED WITH THE TIMING/SHAPE OF THE ENERGY AS IT CONTINUES ACROSS THE SOUTHWEST AND INTO THE CNTRL/E-CNTRL U.S.. LATEST GFS AND ECMWF RUNS ARE ON THE SLOW/FAST EXTREMES OF THE SPREAD RESPECTIVELY WITH THE 00Z UKMET/CMC SOMEWHAT CLOSER TO THE GFS IN TERMS OF TIMING AND CONCENTRATION OF MID LVL ENERGY. SOME EARLIER ECMWF RUNS BEFORE 12Z/23 HAD SOME ROUGH SIMILARITIES TO THE GFS/UKMET/CMC. THERE IS ALSO THE QUESTION OF HOW SHEARED ENERGY IMMEDIATELY UPSTREAM INFLUENCES THE OVERALL EVOLUTION. LACK OF CONFIDENCE IN A PARTICULAR SCENARIO LEADS TO MAINTAINING A FCST CLOSE TO CONTINUITY... DEPICTING A FAIRLY CONSERVATIVE WAVE SLOWER THAN LATEST ECMWF RUNS. IF THE DYNAMICS ARE AS CONCENTRATED AS GFS/UKMET/CMC RUNS CURRENTLY SHOW THE SFC SYSTEM COULD END UP BEING AT LEAST AS STRONG AS THE INITIAL NRN TIER LOW. BROADLY SPEAKING GUIDANCE IS MORE AGREEABLE THAN AVG WITH HGT FALLS REACHING THE WRN STATES BY DAYS 6-7 WED-THU. HOWEVER AS THE SHRTWV APPROACHES THE COAST TUE THE 00Z ECMWF IS STRONGER THAN NEARLY ALL ENSEMBLE GUIDANCE WITH THE LEADING NERN PAC/WRN CANADA RIDGE... THE 00Z GFS IS MOST AGGRESSIVE IN BRINGING ENERGY INTO THE NRN PERIPHERY OF THE RIDGE... AND THE 06Z GFS IS ON THE AMPLIFIED SIDE OF THE SPREAD WITH THE TROUGH. SENSITIVE SHRTWV DETAILS WILL ULTIMATELY DETERMINE HOW MUCH SFC LOW PRES THERE IS NEAR THE WA COAST/VANCOUVER ISLAND BY 12Z WED WHEN THE 06Z GFS/00Z CMC HAVE FAIRLY VIGOROUS SYSTEMS. ONLY A LOW PROPORTION OF 00Z GEFS/ECMWF/CMC ENSEMBLE MEMBERS DEPICT A WELL DEFINED SFC LOW SO AT THIS TIME PREFER TO NUDGE THE FCST TOWARD ONLY A MODEST TRIPLE POINT LOW WHILE AWAITING BETTER AGREEMENT. WHILE THE 00Z/06Z GFS AND 00Z ECMWF EACH OF THEIR QUESTIONABLE TRAITS... A BLEND OF HALF ECMWF AND THE REMAINDER 00Z/06Z GFS YIELDS THE DESIRED INTERMEDIATE FCST FOR DAYS 3-4 SUN-MON. DAY 5 TUE ADDS SOME 00Z GEFS/ECMWF MEAN GUIDANCE TO THE MIX AS A TRANSITION TO DAYS 6-7 WED-THU THAT RELY ON THE MEANS AND 30 PCT CONTINUITY. ...WEATHER HIGHLIGHTS/THREATS... THE WEST WILL SEE PERIODS OF RAIN/HIGHER ELEV SNOW IN ASSOC WITH BUNDLES OF MID LVL ENERGY. EXPECT HIGHEST THOUGH LIKELY NOT EXCEPTIONAL 5-DAY TOTALS TO BE OVER THE PAC NW. CA AND THE SOUTHWEST MAY SEE A PERIOD OF PCPN IN THE FIRST HALF OF THE PERIOD FOLLOWED BY A DRYING TREND AS TRAILING MSTR SHOULD BE LIMITED TO AREAS FROM THE NORTHWEST INTO THE NRN-CNTRL ROCKIES. OVER THE CNTRL-ERN STATES... CONFIDENCE REMAINS FAIRLY HIGH IN ONE OR MORE EPISODES OF HVY RNFL WITHIN AN AREA FROM THE ERN/SERN PLAINS THROUGH THE LOWER HALF OF THE MS VLY INTO THE SOUTHEAST/APLCHNS GIVEN A PERIOD OF ENHANCED GULF INFLOW AND ENERGY ALOFT. HOWEVER UNCERTAINTY IN SPECIFICS SFC/ALOFT FROM ABOUT MON ONWARD ARE MAKING IT DIFFICULT TO PINPOINT THE MOST FAVORED TIMING AND LOCATION OF HIGHEST TOTALS WITHIN THIS BROAD AREA. CONSULT SPC OUTLOOKS FOR LATEST INFO REGARDING STRONG TO SEVERE CONVECTION POTENTIAL... CURRENTLY INDICATED OVER SERN TX INTO LA. SOME COLD SECTOR SNOWFALL IS PSBL OVER THE NRN TIER THOUGH COVERAGE BEHIND THE INITIAL NRN PLAINS LOW MAY BE FAIRLY NARROW. DEPENDING ON STRENGTH OF SFC DEVELOPMENT THERE MAY BE ONE OR MORE PERIODS OF STRONG WINDS OVER THE ERN 2/3 OF THE LOWER 48. CONTINUE TO EXPECT HIGHEST ANOMALIES FOR TEMPS TO BE AHEAD OF THE ADVANCING PLAINS SYSTEM AND TRAILING FRONT WITH A DECENT AREA SEEING MIN/MAX READINGS AT 10-20F ABOVE NORMAL AND PERHAPS LOCALLY HIGHER. THERE MAY BE A FEW LOCATIONS WITH RECORD WARM MINS. COLD ANOMALIES BEHIND THE SYSTEM SHOULD BE MORE MODEST WITH ONLY A FEW POCKETS MORE THAN 10F BELOW NORMAL OVER THE WEST/ROCKIES. RAUSCH