EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 245 AM EDT MON OCT 10 2016 VALID 12Z THU OCT 13 2016 - 12Z MON OCT 17 2016 ...PATTERN OVERVIEW... GUIDANCE IS CONSISTENT IN DEPICTING A DEEP ERN PACIFIC MEAN TROUGH ALOFT THAT WILL PROMOTE VERY ACTIVE WEATHER OVER THE NWRN U.S.. AT THE SAME TIME PROGRESSIVE AND GENERALLY LOW AMPLITUDE MEAN FLOW DOWNSTREAM WILL CARRY ALONG FEATURES THAT WILL GENERATE SOME AREAS OF RNFL BUT WITH AMTS MUCH LESS EXTREME THAN THOSE ANTICIPATED OVER THE NORTHWEST. ...GUIDANCE/UNCERTAINTY EVALUATION ... AS OF THE 12Z/18Z CYCLES THE MODELS AND ENSEMBLE MEANS WERE SUFFICIENTLY AGREEABLE FOR SIGNIFICANT FEATURES TO ALLOW A CONSENSUS BLEND THROUGH THE PERIOD. THIS BLEND INCORPORATES THE 12Z/18Z GFS ALONG WITH THE 12Z ECMWF/UKMET DAYS 3-5 THU-SAT... AND THE 12Z-18Z GFS/12Z ECMWF ALONG WITH THE 18Z GEFS/12Z ECMWF MEANS DAYS 6-7 SUN-MON AS SOME OPERATIONAL MODEL DETAILS BEGIN TO DIVERGE A LITTLE MORE. LATEST SOLNS ARE STARTING TO GAIN SOME CLARITY ON ERN PAC/WEST COAST DETAILS. A LEADING STRONG SFC LOW BEGINS TO DEVELOP FROM FLAT NRN PAC FLOW LATE IN THE SHORT RANGE AND THEN MAY TRACK NEAR VANCOUVER ISLAND BY DAY 4 FRI. 12Z/18Z GFS RUNS ARE A BIT ON THE SRN SIDE OF THE FULL GUIDANCE SPREAD... AND FOR THE TIME BEING THE 00Z GFS APPEARS TO CONFIRM PREFS TOWARD A MORE INTERMEDIATE TRACK. THE NEXT SYSTEM FOLLOWING CLOSE BEHIND AROUND SAT MAY WELL BE AT LEAST AS STRONG IF NOT STRONGER AS IT ORIGINATES FROM TROPICAL CYCLONE SONGDA WHICH IS CURRENTLY IN THE WRN PAC. ESPECIALLY FOR THIS SECOND SYSTEM THE NEW 00Z GUIDANCE AVBL THUS FAR SEEMS TO INCREASE CONFIDENCE IN A DEEPER LOW THAN WHAT WAS GENERATED BY THE PREFERRED BLEND. TOWARD DAYS 6-7 SUN-MON THE ENSEMBLES BEGIN TO DIFFER IN OPINION ON THE SHAPE/POSN OF FEATURES WITHIN THE ERN PAC MEAN TROUGH AND THE SHAPE OF DOWNSTREAM CONUS FLOW. SPECIFICALLY THERE ARE SOME INDICATIONS TOWARD INCREASED CNTRL U.S. RIDGING... SOMEWHAT MORE PREVALENT IN GFS/GEFS SOLNS. OVER THE PAST 24 HRS THE ECMWF MEAN HAS WEAKENED ITS CNTRL U.S. RIDGE SOMEWHAT WHILE THE GEFS MEAN HAS TRENDED STRONGER SO AN INTERMEDIATE SOLN SEEMS BEST AT THIS TIME. FARTHER EWD GUIDANCE HAS BECOME STRONGER AND BETTER CLUSTERED WITH THE DAY 5 SAT LOW PRES OVER SRN CANADA IN RESPONSE TO EJECTING ERN PAC/WRN U.S. ENERGY... WITH A TRAILING FRONT EXTENDING INTO THE LOWER 48. AHEAD OF THIS EVOLUTION MODELS ARE STILL HAVING SOME DIFFICULTIES IN RESOLVING SPECIFICS OF A DIFFUSE SHRTWV TRACKING OUT OF THE SWRN STATES THU ONWARD. GENERAL TRENDS FROM THE PAST COUPLE DAYS HAVE BEEN TO DELAY THE SEPARATION OF EMBEDDED ENERGY IF IT OCCURS. ...WEATHER HIGHLIGHTS/THREATS... AT LEAST TWO VERY STRONG SFC LOWS OFFSHORE THE PAC NW/VANCOUVER ISLAND WILL LIKELY PRODUCE PERIODS OF STRONG WINDS OVER THE PAC NW AND HELP TO FOCUS ABUNDANT MOISTURE ACROSS THE CNTRL-NRN WEST COAST INTO THE NRN ROCKIES. CURRENT GUIDANCE SUGGESTS THAT SOME LOCATIONS FROM NRN CA THROUGH WRN WA/OR COULD SEE 5-DAY TOTALS LOCALLY REACHING AT LEAST 10-15 INCHES... HIGHEST ALONG THE COAST NEAR THE OR/CA BORDER. LESS EXTREME BUT STILL MULTI-INCH TOTALS ARE PSBL OVER THE NRN ROCKIES. EXPECT SNOW LVLS TO BE QUITE HIGH THROUGH THE PERIOD. FARTHER EWD THE S-CNTRL PLAINS INTO THE GRTLKS SHOULD BE THE MOST PROMINENT AXIS FOR RNFL. A LEADING FRONT AT THE START OF THE PERIOD THU WILL BRING A WEAKENING AREA OF PCPN TO THE GRTLKS/INTERIOR NORTHEAST. COMBINATION OF WEAK SHRTWV ENERGY EMERGING FROM THE WEST AND A LINGERING SRN PLAINS SFC FRONT WILL LIKELY PRODUCE ONE AREA OF PCPN FROM THE SRN PLAINS INTO OR NEAR THE OH VLY LATE WEEK INTO THE WEEKEND. TODAY THERE IS SOMEWHAT BETTER AGREEMENT IN THE GUIDANCE THAT MOST OF THIS ACTIVITY SHOULD DIMINISH BEYOND THE APLCHNS. THEN FROM THE WEEKEND INTO EARLY NEXT WEEK A FRONTAL SYSTEM SHOULD SUPPORT AN AREA OF RNFL FROM THE MS VLY INTO OH VLY/GRTLKS. CHILLY PLAINS/MS VLY HIGH PRES WILL MODIFY AS IT HEADS TOWARD THE EAST COAST. BEHIND THIS HIGH EXPECT AN INCREASINGLY BROAD AREA OF ABOVE NORMAL TEMPS FROM THE CNTRL-SRN ROCKIES EWD WITH CONSIDERABLE COVERAGE OF PLUS 10F OR GREATER ANOMALIES. ISOLD DAILY RECORDS ARE PSBL WITH BEST POTENTIAL FOR MAX TEMPS OVER PARTS OF THE SRN TIER AND MAYBE EXTENDING A LITTLE FARTHER NWD FOR WARM MINS. RAUSCH