EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 200 AM EST FRI DEC 04 2015 VALID 12Z MON DEC 07 2015 - 12Z FRI DEC 11 2015 ...A WET NORTHWEST... ...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER HIGHLIGHTS/THREATS... THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A COMBINATION OF THE 12 UTC ECMWF ENSEMBLE MEAN AND WPC/NDFD CONTINUITY...WITH A SMALL CONTRIBUTION FROM THE GEFS/NAEFS MEANS TO INCORPORATE ALTERNATE POSSIBILITIES. THE ECMWF ENSEMBLE MEAN WAS THE MOST COMPATABLE ENSEMBLE TO YESTERDAYS WPC CONTINUITY INTO EARLY NEXT WEEK AND MOST IN LINE WITH FICKLE MODEL TRENDS BY LATER NEXT WEEK...HENCE THE GREATER FORECAST WEIGHTING. DETERMINISTIC MODEL GUIDANCE FROM THE 12/18 UTC CYCLE OFFERED MUCH MORE FORECAST SPREAD THAN RECENT PRIOR CYCLES AND WAS ACCORDINGLY DOWNPLAYED...WITH MUCH UNCERTAINTY ASSOCIATED WITH TRENDS TO AND AWAY FROM SYSTEM PROGRESSION. CURRENT WATER VAPOR IMAGERY UPSTREAM OVER THE PACIFIC SHOWS SOME AMPLIFIED SYSTEMS THAT CAN PROVE SLOW TO TRANSLATE...BUT ALSO AMPLE JET FLOW TO KEEPS THINGS MOVING. PREDICTABILITY IN THIS FLOW IS BELOW NORMAL DAYS 3-7. THERE IS SOME POTENTIAL FOR ERN US COASTAL SURFACE CYCLOGENESIS OF SOME MAGNITUDE EARLY NEXT WEEK WITH APPROACH OF A AMPLIFIED LEAD MID-UPPER LEVEL TROUGH...BUT TEMPS ARE MODERATE FOR DECEMBER WITH PASSAGE AND TIMING REMAINS UNCERTAIN. DESPITE GREATER THAN NORMAL OVERALL FLOW UNCERTAINTY...SOME ASPECTS OF THE FORECAST ACTUALLY OFFER ABOVE NORMAL PREDICTABILITY. THIS INCLUDES THE LIKELIHOOD THAT A ENERGETIC SUPPLY OF POTENT PACIFIC SYSTEMS WILL FOCUS INLAND INTO THE NORTHWESTERN US TO PRODUCE MULTIPLE PERIODS ENHANCED WIND AND PCPN OVER THE NEXT WEEK OR MORE. THIS PATTERN WILL OFFER SUBSTANTIAL UNSETTLING HEIGHT FALLS ACROSS THE WRN US AND INTO THE CENTRAL US NEXT WEEK THAT LEAD TO AMPLE DOWNSTREAM ERN US HEIGHT RISES. SCHICHTEL