ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 323 PM EDT SAT SEP 10 2016 VALID 12Z WED SEP 14 2016 - 12Z SUN SEP 18 2016 OVERALL THE GUIDANCE IS IN DECENT AGREEMENT THROUGH NEXT THURS/FRI FOR AK WITH SPREAD INCREASING INTO NEXT WEEKEND. MANUAL PROGS BLENDED THE 12Z GFS AND THE 06Z GEFS MEAN WITH YESTERDAY'S 12Z ECMWF AND TODAY'S 00Z ECMWF/ECMWF ENSEMBLE MEAN. DURING MID WEEK... A CLOSED LOW SLOWLY DRIFTS UP THE SPINE OF THE ALEUTIAN ISLAND CHAIN. A POSITIVELY TILTED TROUGH CROSSES NORTHWEST AK WITH HIGHER HEIGHTS/ADJUSTED SEA LEVEL PRESSURES OVER THE PANHANDLE. IN BETWEEN...A WELL DEFINED FRONT PERSISTS IN EAST CENTRAL AK WITH WAVES OF LOW PRESSURE MOVING ALONG THE FRONT. BY 12Z FRI...THE MODELS/ENSEMBLE CLUSTER SHOWS THE LOW PRESSURE IN THE UPPER ALEUTIANS AND ADJACENT SOUTHWEST AK/FAR NORTHERN PACIFIC. A TREMENDOUS INFLUX OF PAC MOISTURE WITH PWS 1.5 STANDARD DEVIATIONS ABOVE NORMAL WILL MAINLY FOCUS ACROSS THE SRN/SERN TIER OF THE STATE. THE FRONT PERSISTS OVER CENTRAL AK AND A RIDGE REMAINS ACROSS COASTAL SOUTHEAST AK/PANHANDLE. THE BIG CYCLONE COMING OUT OF THE ALEUTIANS MOVES IN COASTAL SOUTHERN AK AND/OR ADJACENT KODIAK ISLAND/FAR NORTHERN GULF OF AK. THE FRONT IN INTERIOR AK DRIFTS SLOWLY NORTH...WITH LOW PRESSURE CENTERS SPREAD ACROSS NORTHWEST AK WITH LITTLE OVERLAP AMONG THE 12-00Z ECMWF/06Z GFS AND 00 ECMWF ENSEMBLE MEAN/00Z CANADIAN GLOBAL FORECASTS. THE 12Z ECMWF THROWS A WRINKLE IN WITH STRONGER LOW PRESSURE DEVELOPING OFF THE WEST COAST OF AK 00-12Z SAT. ON NEXT SUN 18 SEP...CLUSTERING REMAINS GOOD AROUND THE SLOWLY DECAYING LOW PRESSURE REMAINING IN SOUTHERN AK. THE WIDE SPREAD OF WHERE LOW PRESSURE CENTERS ARE CONTINUES ACROSS NORTHERN AK AND THE ADJACENT COASTAL WATERS BOTH OFF NORTHERN AK AND INTO THE BERING STRAITS AND BERING SEA. THIS LEADS TO THE PREFERENCE TO GIVE LOW WEIGHT TO EACH SOLUTION BUT NOT A LOT OF WEIGHT BECAUSE OF DISAGREEMENTS FROM MODEL TO MODEL AND RUN TO RUN...PLUS DISAGREEMENTS BETWEEN THE MODELS AND THEIR RESPECTIVE ENSEMBLE MEANS. THE 12Z ECMWF MOVED LOW PRESSURE FROM SOUTH OF THE ALEUTIANS TO NORTH OF THE ISLAND CHAIN 12Z SUN 18 SEP..CLOSER TO THE ENSEMBLE MEAN AXIS/ORIENTATION. CONSEQUENTLY...A CONSENSUS BASED APPROACH WAS USED...INCORPORATING THE AFOREMENTIONED MODELS AND ENSEMBLE MEANS WITHOUT STAGGERING THE PREFERENCE TOWARDS ANY ONE SOLUTION. THIS APPROACH PROVIDES PRETTY GOOD CONTINUITY THROUGH THE MIDDLE PORTION OF NEXT WEEK...AS THE OVERALL DISTRIBUTION OF SOLUTIONS HAS NOT CHANGED MUCH...WITH THE DAYS 4-5 CYCLONE MOVING UP THE ALEUTIANS HAVING EXCELLENT CONTINUITY FROM YESTERDAY'S FORECAST. PETERSEN