ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 228 PM EDT FRI AUG 29 2014 VALID 12Z TUE SEP 02 2014 - 12Z SAT SEP 06 2014 THE ALASKAN FLOW PATTERN REMAINS HIGHLIGHTED BY A SIGNIFICANT ARCTIC VORTEX NEAR THE NORTH SLOPE NEXT WEEK ALLOWING FOR A PROLONGED PERIOD OF UPPER-LEVEL TROUGHING FROM THE ARCTIC OCEAN THROUGH THE INTERIOR. EXPECT BELOW NORMAL TEMPS FOR MUCH OF ALASKA AS 500/700 MB HEIGHT ANOMALIES WILL CENTER 2-3 STANDARD DEVIATIONS BELOW NORMAL NORTH OF THE ARCTIC CIRCLE. THE PATTERN SHOULD ALLOW MODEST LINGERING IMPULSES AND SURFACE DEVELOPMENT UNDERNEATH OVER THE ALASKAN SRN/SERN TIER BOTH OVER/FROM THE GULF OF AK AND LATE WEEK UPSTREAM SOUTH OF THE ALEUTIANS. THE 00 UTC ECMWF IN PARTICUALAR SHOWS MORE STREAM INTERACTION/PHASING THAN COMPARED TO OTHER DETERMINISTIC MODELS UP INTO THE BERING SEA/SW ALASKA NEXT WEEK...BUT THIS DOES NOT SEEM SUPPORTED AT THIS POINT ENOUGH BY ENSEMBLES OR WATER VAPOR LOOPS TO EMBRACE. A QUICK PEEK AT THE NEWER 12 UTC ECMWF STILL SHOWS PHASING BUT WITH LESS VIGOR. GIVEN DETERMINISTIC UNCERTAINTY...THE WPC ALASKAN MEDIUM RANGE PRODUCT SUITE HAS BEEN DERIVED FROM AN ENSEMBLE MEAN FORECAST APPROACH. THE 00 UTC GFS ENSEMBLE MEAN WAS PRIMARILY USED AS BEST MAINTAINS PATTERN CONTINUITY WITH EMBEDDED FEATURES WHILE REMAINING REASONABLY COMPATABLE...ESPECIALLY ALOFT...WITH 00 UTC ECMWF/NAEFS ENSEMBLE MEANS. SCHICHTEL