EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1153 AM EDT SAT OCT 08 2016 VALID 12Z TUE OCT 11 2016 - 12Z SAT OCT 15 2016 ...A HEAVY RAINFALL PATTERN EMERGES INTO THE NWRN US... ...PATTERN OVERVIEW... GUIDANCE SHOWS GENERALLY PROGRESSIVE MEAN FLOW OVER MUCH OF THE LOWER 48 NEXT WEEK AS AN MID-UPPER LEVEL TROUGH BECOMES ESTABLISHED OVER THE ERN PACIFIC. MULTI-DAY MEANS CENTERED ON DAY 8 STILL SHOW A STRONG CORE OF NEGATIVE HEIGHT ANOMALIES ABOUT 10-20 DEGS LONGITUDE OFFSHORE THE PAC NW. ASSOCIATED TELECONNECTIONS SUPPORT THE WET REGIME FORECAST FOR THE CENTRAL-NRN WEST COAST BY THE MODELS/ENSEMBLES. FARTHER EWD CONTINUE TO EXPECT A FRONT TO PUSH SEWD FROM THE PLAINS/UPPER MS VALLEY TUE ONWARD ACROSS THE SRN AND ERN US INTO LATE WEEK WHILE A SIGNIFICANTLY WEAKENED MATTHEW GETS ABSORBED OVER THE WRN ATLANTIC INSTEAD OF LOOPING TOWARD THE BAHAMAS AS PER THE LATEST FROM THE NHC. THE 00 UTC UKMET DOES OFFER AN OUTLIER NEW ENG US THREAT...SHOWING HOW SENSITIVE THE MODELS REMAIN TO INITIALIZATION. ...GUIDANCE EVALUATION... LEADING ERN PAC ENERGY HEADING INTO THE WRN STATES WED-THU STILL SHOWS SOME DETAIL DIFFS BUT WITH LESS NOTICEABLE IMPACT ON THE SFC PATTERN THAN RECENTLY. THERE IS AGREEMENT IN PRINCIPLE THAT ENERGY CARRIED ALONG BY ALASKAN BLOCK UNDERCUTTING NRN PAC FLOW SHOULD DEVELOP A FAIRLY DEEP SYSTEM OFFSHORE THE PAC NW/VANCOUVER ISLAND THU-FRI AND ANOTHER SYSTEM MAY FOLLOW CLOSE BEHIND. SOME MODEL RUNS THAT HAVE BEEN BRINGING ONE OR BOTH FEATURES FAIRLY CLOSE TO VANCOUVER ISLAND ARE ACCEPTABLY WITHIN THE FULL ENSEMBLE SPREAD THOUGH ENOUGH MEMBERS REMAIN FARTHER SWD/WWD TO KEEP THE MEANS MORE OFFSHORE. DURING THE PAST DAY OR TWO CONSENSUS HAS TRENDED SOMEWHAT SHARPER/DEEPER/SLOWER WITH THE UPR TROUGH CROSSING THE NRN TIER STATES. THIS ADJUSTMENT ALLOWS THE LEADING COLD FRONT TO PULL UP A LITTLE MORE MSTR THAN PREVIOUSLY FORECAST AND PUSH FARTHER SWD OVER THE PLAINS. BEHIND THIS UPPER TROUGH/SURFACE FRONT THE FORECAST LOSES CLARITY ALOFT AS MODELS/ENSEMBLE MEMBERS SHOW A VARIETY OF POSSIBILITIES FOR INCOMING PAC ENERGY CROSSING THE LOWER 48. THE FAIRLY SIMILAR MEANS OFFER THE BEST OPTION FOR SIDESTEPPING SHROTWAVES THAT HAVE LOW PREDICTABILITY IN PROGRESSIVE MEAN FLOW. OVERALL...THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A COMPOSITE GUIDANCE SOLUTION HEAVY ON ENSEMBLE MEAN GUIDANCE CONSISTENT WITH UNCERTAINTY. ...WEATHER HIGHLIGHTS/THREATS... EXPECT MOISTURE BEGIN REACHING THE NRN HALF OF THE WEST COAST LATER WED WITH A DEEPER CONNECTION AND HEAVIER ACTIVITY LIKELY TO BUILD THU INTO NEXT WEEKEND. EXPECT PCPN TO FLUCTUATE IN INTENSITY BASED ON EVOLUTION OF INDIVIDUAL SYSTEMS OFFSHORE...LIKELY CONTINUING BEYOND NEXT SAT. HIGHEST TOTALS SHOULD EXTEND FROM NRN CA THROUGH FAVORED TERRAIN OF THE PAC NW WHILE SIGNIFICANT THOUGH LESSER AMOUNTS REACH INLAND TO THE NRN ROCKIES. SNOW LEVELS WILL LIKELY BE QUITE HIGH. ONE OR MORE PERIODS OF ENHANCED WINDS ARE ALSO POSSIBLE OVER THE PAC NW THU ONWARD DEPENDING ON STRENGTH/TRACK OF THE ERN PAC LOWS. RAINFALL WILL ACCOMPANY THE COLD FRONT PUSHING SEWD FROM THE PLAINS/UPPER MS VALLEY TUE ONWARD. WHAT ENHANCEMENT THERE IS SHOULD BE FAIRLY LOCALIZED OVER THE E-CENTRAL US. THIS SUPPORTS A SWATH OF POST-FRONTAL COOLING. BY LATE WEEK THE CENTRAL U.S. MAY SEE ANOTHER AREA OF RAINFALL DEVELOP IN RESPONSE TO UPSTREAM ERN PAC ENERGY PASSAGE. THE FLORIDA PENINSULA SHOULD SEE PERIODS OF RAINFALL WITH PERSISTENT NERLY LOW LEVEL ONSHORE FLOW. SCHICHTEL