EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1056 AM EST TUE DEC 02 2014 VALID 12Z FRI DEC 05 2014 - 12Z TUE DEC 09 2014 ...GUIDANCE/UNCERTAINTY ASSESSMENT AND SENSIBLE WEATHER HIGHLIGHTS... THE LATEST MODELS AND ENSEMBLES OFFER A REASONABLY SIMILAR AND ACTIVE LARGER SCALE FLOW PATTERN EVOLUTION OVER MUCH OF THE NEXT WEEK...BOLSTERING FORECAST CONFIDENCE. HOWEVER...A MULTITUDE OF LESS PREDICTABLE AND VARIED AMPLITUDE SMALL-MID SCALE NRN AND SRN STREAM SHORTWAVES EMBEDDED WITH THE FLOW PROGRESS OVER NORTH AMERICA DOWNSTREAM OF AN ANCHORING NERN PACIFIC MID-UPPER LEVEL TROUGH. THE TIMING OF THESE FEATURES AND POTENTIAL ASPECTS OF ANY STREAM PHASING REMAIN MORE UNCERTAIN. ACCORDINGLY PREFER AN PREDOMINANTLY ENSEMBLE MEAN BASED SOLUTION TO MITIGATE SOME OF THE SMALL TO MID SCALE UNCERTAINTY. LEANED ON THE 00 UTC ECMWF ENSEMBLE MEAN INTO FRI/SAT THAT OF THE ENSEMBLE SOLUTIONS SEEMS TO BEST MATCH WITH SEEMINGLY REASONABLE WPC OVERNIGHT MODEL DIAGNOSTIC DESK PMDHMD PREFERENCES...ESPECIALLY FROM THE ERN PACIFIC INTO THE WRN US THAT ALSO FAVORED SOME INFLUENCE FROM THE 00 UTC ECMWF/CANADIAN INTO THESE EARLY MEDIUM RANGE FRAMES IN CONTRAST TO THE MORE SOUTHWARD SHIFTED 00 UTC GFS. INSTEAD MIXED THE 00 UTC ECMWF ENSEMBLE MEAN WITH SOME COMPATABLE 06 UTC GFS ENSEMBLE MEAN AT LONGER TIME FRAMES LATER WEEKEND INTO EARLY NEXT WEEK. THIS OFFERED BETTER CONTINUITY CONSISTENT WITH GROWING UNCERTAINTY. NRN AND SRN STREAM FLOWS OVER NORTH AMERICA SHOULD TEND TO AMPLIFY OVER TIME GIVEN THE SETTLED UPSTREAM NERN PACIFIC MID-UPPER LEVEL TROUGH POSITION. THIS PATTERN SHOULD PROVIDE SYSTEMS FOR A PROTRACTED WET PERIOD ACROSS THE NWRN US WITH SYSTEM APPROACH/PASSAGE AND AN EMERGING DOWNSTREAM WET PATTERN FROM THE E-CENTRAL TO ERN US. WHILE FLOW EVOLUTION DOES OFFER SOME POTENTIAL FOR SOME STREAM PHASING AND COASTAL LOWS FARTHER EAST...THE TIMING OF EMBEDDED SHORTWAVES IS TOO UNCERTAIN TO DETERMINISTICALLY DEPICT FEATURES WITH MUCH UMPH. SCHICHTEL