EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 112 AM EST SUN DEC 06 2015 VALID 12Z WED DEC 09 2015 - 12Z SUN DEC 13 2015 ...A NWRN US HEAVY PRECIPITATION PATTERN... ...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER HIGHLIGHTS/THREATS... THE WPC MEDIUM RANGE PRODUCT SUITE IS PRIMARILY DERIVED FROM REASONABLY COMPATABLE GUIDANCE FROM 12 UTC ECMWF ENSEMBLE MEAN AND NAEFS MEAN. PREFER AN ENSEMBLE MEAN FORECAST APPROACH AS RECENT DETERMINISTIC MODELS HAVE BEEN RUN TO RUN INCONSISTENT. A SERIES OF PROGRESSIVE AND POTENT PACIFIC SYSTEMS WILL SLAM INTO THE NWRN US/NRN CA AND WORK ACROSS THE LOWER 48/SRN CANADA THIS WEEK. PREDICTABILITY SEEMS BELOW NORMAL WITH SYSTEM TIMING AND SPECIFICS GIVEN FORECAST SPREAD...BUT EACH SHOULD FOCUS WINDS AND PCPN IN AN ENERGETIC PATTERN. DESPITE GREATER THAN NORMAL OVERALL FLOW UNCERTAINTY...SOME ASPECTS OF THE FORECAST INTO LONGER TIME FRAMES STILL SEEMS TO OFFER SOME ABOVE NORMAL PREDICTABILITY. ENHANCED INFLOW INTO NW US/NRN CA WILL FUEL MULTIPLE PERIODS WITH ENHANCED WIND AND EXCESSIVE PRECIPITATION. A HEAVY SNOW THREAT WILL FOCUS INLAND ACROSS FAVORED TERRAIN OF THE N-CENTRAL INTERMOUNTAIN W/ROCKIES. THIS PATTERN WILL OFFER SUBSTANTIAL UNSETTLING HEIGHT FALLS FROM THE WRN US TO THE CENTRAL US NEXT WEEK. THIS WILL LEAD TO AMPLE DOWNSTREAM CENTRAL TO ERN US HEIGHT RISES/WARMING IN ADVANCE OF SYSTEMS...WITH MAIN WRN US MID-UPPER LEVEL TROUGHING MORE ERNESTLY SUPPORTING AN INCREASING FAVORABLE GULF INFLOW/RAIN PATTERN TO THE E-CENTRAL US NEXT WEEKEND WITH CYCLO/FRONTOGENESIS. SCHICHTEL