EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1059 AM EST TUE JAN 05 2016 VALID 12Z FRI JAN 08 2016 - 12Z TUE JAN 12 2016 ...OVERVIEW... MULTI-DAY MEANS SHOW A BROAD AREA OF ABOVE NORMAL HGTS ALOFT ACROSS THE HIGHER LATITUDES... SUPPORTING BELOW NORMAL HGTS ACROSS MUCH OF THE LOWER 48 AND CNTRL-ERN PACIFIC. DOMINANT TROUGHS WILL BECOME ESTABLISHED OVER THE ERN 2/3 OF NOAM AND E-CNTRL PAC WHILE HGTS MAY BE CLOSER TO AVG VALUES WITHIN A MEAN RIDGE ALONG/INLAND FROM THE WEST COAST. HOWEVER THIS RIDGE SHOULD STILL BE WEAK ENOUGH TO ALLOW OCCASIONAL PASSAGE OF SOME ERN PAC ENERGY THAT SPLITS OFF FROM REMAINING FLOW THAT IS DIVERTED AROUND THE WRN SIDE OF THE NWD EXTENSION OF THE WEST COAST RIDGE. ...GUIDANCE EVALUATION/WPC PREFERENCES... FROM DAY 3 FRI INTO DAY 4 SAT PREFER A CONSENSUS APPROACH WITH PRIMARY EMPHASIS ON OPERATIONAL GUIDANCE... THE 00Z-06Z GFS AND 00Z ECMWF. THIS BLEND LEANS AWAY FROM THE 00Z GFS THAT IS SLOWER THAN CONSENSUS WITH THE SRN HALF OF THE SYSTEM NEARING THE WEST COAST AS OF EARLY SAT WHILE DOWNPLAYING THE 06Z GFS THAT BY SAT BECOMES SOMEWHAT N/W OF THE GUIDANCE MAJORITY WITH THE SYSTEM REACHING THE GRTLKS. BY SAT THE ENSEMBLE ENVELOPE FOR THIS GRTLKS SYSTEM HAS NOT NARROWED VERY MUCH OVER THE PAST DAY THOUGH CONSENSUS HAS SHOWN A BIT OF A FASTER TREND. SMALL SCALE WAVINESS ALONG THE EAST COAST HAS CONSIDERABLE SPREAD AND WILL LIKELY TAKE FURTHER TIME TO BE RESOLVED. THERE IS STILL A FAIR AMOUNT OF UNCERTAINTY WITH ERN CONUS SFC EVOLUTION MID-LATE PERIOD IN ASSOC WITH THE COMBINATION OF SRN STREAM ENERGY REACHING THE PLAINS SAT AND CONTINUING NEWD THEREAFTER ALONG WITH DEEP CYCLONIC FLOW EXTENDING INTO THE NRN HALF OF THE CONUS FROM SRN CANADA. INDIVIDUAL ENSEMBLE MEMBERS DISPLAY ABOUT AS MUCH SCATTER AS 24 HRS AGO. CONSECUTIVE OPERATIONAL RUNS FROM THE GFS/ECMWF HAVE BEEN QUITE VARIABLE WITH THE DETAILS WHILE LIKE THE OPERATIONAL RUNS THE 00Z GEFS AND ECMWF MEANS HAVE TRENDED NOTICEABLY FASTER WITH OVERALL EVOLUTION. THIS FASTER TREND APPEARS TO CORRESPOND TO A SEWD ADJUSTMENT IN THE SRN CANADA/NRN CONUS TROUGH. ASSUMING THE TREND WITH THE NRN STREAM TROUGH IS CORRECT... A FASTER TREND SEEMS REASONABLE GIVEN A TIGHTER GRADIENT FARTHER EWD. THUS WILL ACCEPT MOST OF THE ENSEMBLE MEAN ADJUSTMENTS THOUGH INCLUDING ABOUT 60 PCT TOTAL OF THE 06Z GEFS/00Z NAEFS MEANS THAT ARE SLIGHTLY SLOWER ECMWF MEAN. WITHIN THE NRN STREAM TROUGH MADE SOME EDITS TO ADJUST TOWARD A BETTER DEFINED UPR LOW THAN DEPICTED IN THE MEANS BUT NWD OF THE 00Z ECMWF AND SLOWER THAN THE 00Z-06Z GFS. WEST COAST DIFFS ARE LESS SIGNIFICANT IN THE LARGE SCALE BUT WILL STILL BE IMPORTANT LOCALLY. MAIN ENHANCEMENT TO THE MEANS WOULD BE AROUND DAYS 6-7 MON-TUE WHEN OPERATIONAL GUIDANCE HINTS MORE AT SOME ERN PAC ENERGY HEADING INTO THE WRN MEAN RIDGE. PARTIAL INCLUSION OF THE OPERATIONAL SCENARIO SEEMS REASONABLE GIVEN THE ONGOING TENDENCY FOR SRN STREAM IMPULSES TO REACH THE WRN STATES. ...SENSIBLE WEATHER HIGHLIGHTS... BELOW NORMAL TEMPS ACROSS MUCH OF THE WEST AND NRN-CNTRL PLAINS TO START THE PERIOD SHOULD PERSIST OVER THOSE AREAS AND PUSH STEADILY EWD WITH TIME. CANADIAN HIGH PRESSURE DROPPING INTO THE NRN PLAINS SHOULD SUPPORT COLDEST DAYTIME HIGHS OF 20-30F BELOW NORMAL AT SOME LOCATIONS ON SAT. OTHERWISE EXPECT MULTIPLE DAYS WITH HIGHS 10-20F BELOW NORMAL ACROSS THE NRN TIER AND ALSO EXTENDING FARTHER SWD INTO THE PLAINS DURING THE WEEKEND. WRN CONUS ANOMALIES WILL LIKELY BE IN THE MINUS 5-15F RANGE. FROM FRI INTO THE WEEKEND ERN STATES WILL SEE ONE OR MORE DAYS OF PLUS 10-20F ANOMALIES FOR HIGHS AND UP TO PLUS 20-30F ANOMALIES FOR LOWS... WITH ISOLD RECORD WARM LOWS PSBL. COLD AIR REACHING THE EAST BY EARLY NEXT WEEK SHOULD BRING TEMPS DOWN TO 5-10F BELOW NORMAL. SYSTEMS AFFECTING THE CNTRL-ERN STATES EARLY-MID PERIOD WILL TEND TO FAVOR BEST PROBABILITY FOR WINTRY PRECIP FROM THE CNTRL PLAINS INTO GRTLKS... PSBLY FOR A TIME OVER NEW ENGLAND BEFORE ARRIVAL OF WARMER AIR. LATEST TRENDS HAVE RAISED THE PROPORTION OF RAIN VS SNOW WITH THE SYSTEM AFFECTING THE NORTHEAST AROUND SUN-MON. BY EARLY NEXT WEEK COLD FLOW BEHIND COMPLEX ERN CONUS DEVELOPMENT WILL SUPPORT LAKE EFFECT SNOW WHICH MAY BE HVY AT SOME LOCATIONS. THE WEST WILL SEE PERIODS OF COASTAL/LOW ELEV RAIN AND HIGHER ELEV SNOW WITH INDIVIDUAL IMPULSES PASSING THROUGH THE MEAN RIDGE ALOFT. AMTS SHOULD BE ON THE LGT-MDT SIDE IN MOST CASES. RAUSCH