ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 331 PM EDT SAT JUN 10 2017 VALID 12Z WED JUN 14 2017 - 12Z SUN JUN 18 2017 MODEL PREFERENCES/PATTERN OVERVIEW... THE INITIAL SET UP ACROSS THE REGION WILL FEATURE A BROAD UPPER HIGH EXTENDING FROM NORTHWESTERN AK INTO THE CHUKCHI SEA. TO THE SOUTH OF THIS POSITIVE HEIGHT ANOMALY...A PAIR OF UPPER LOWS WILL BE THE MAIN FEATURES TO TRACK. AS THE HIGHER LATITUDE RIDGE RETROGRADES AND WEAKENS A BIT...THE LEAD UPPER LOW BEGINS TO LIFT OUT OF THE GULF OF AK TOWARD THE YUKON TERRITORY. THIS PARTICULAR FEATURE CONTAINS MUCH OF THE MODEL SPREAD DURING THE PERIOD...MOSTLY WITH REGARDS TO TIMING. THE PAST SEVERAL RUNS OF THE GFS HAVE FAVORED A SLOWER FORWARD PROGRESSION WHICH MAINTAINS FLATTER UPSTREAM FLOW. THIS IS IN STARK CONTRAST WITH THE 00Z ECMWF WHICH IS MORE PROGRESSIVE THEREBY ALLOWING HEIGHTS TO BUILD IN ADVANCE OF THE NEXT SYSTEM CROSSING SOUTH OF THE ALEUTIANS. THERE IS SOME SPATIAL WEST-EAST ORIENTED SPREAD WITH THIS LATTER SYSTEM...BUT ALL SOLUTIONS DEPICT IT TO VARYING DEGREES. THE PREFERRED SOLUTION PLAYED A MIDDLE GROUND APPROACH GIVEN EACH MODEL SEEMS TO BE FAIRLY CONSISTENT WITH ITSELF. THROUGH DAY 6/FRIDAY...TOOK A BALANCE OF THE 12Z GFS/06Z GEFS MEAN WITH THE 00Z ECMWF/ECMWF ENSEMBLE MEAN WITH INCREASING INFLUENCES OF THE MEANS DEEPER INTO THE FORECAST. FOR DAYS 7/8...WENT 100 PERCENT WITH ENSEMBLE MEANS WITH SOME INCLUSION OF THE 00Z NAEFS MEAN TO INCORPORATE SOME MODEL DIVERSITY. WEATHER IMPACTS... THROUGHOUT THE FORECAST PERIOD...THE MILDEST CONDITIONS SHOULD BE ACROSS INTERIOR SECTIONS OF AK. IT LOOKS LIKE WIDESPREAD HIGHS IN THE 60S WILL BE THE NORM WITH PERHAPS A FEW AREAS IN THE LOW 70S. TEMPERATURES ALONG THE SOUTHERN AK COAST SHOULD BE ABOUT 10 TO 15 DEGREES COOLER WHERE HIGHER CHANCES OF PRECIPITATION AND DENSER COVERAGE OF CLOUDS WILL BE LIKELY. AS USUAL...THE COOLEST CONDITIONS SHOULD BE ACROSS NORTHERN AK WHERE ANY ONSHORE COMPONENT OF THE WIND WILL HOLD READINGS CLOSER TO THE LOW 40S. IN TERMS OF PRECIPITATION THREATS...SOUTHEASTERN AK SHOULD SEE THE MOST PERSISTENT CHANCES FOR RAINFALL GIVEN THE SLUG OF ONSHORE FLOW HITTING THE COAST. A BIT FARTHER INLAND ACROSS SOUTH-CENTRAL AK...THERE SHOULD BE ENOUGH INSTABILITY BASED ON THE LIFTED INDEX PARAMETER TO SUPPORT SOME POCKETS OF SHOWERS/THUNDERSTORMS. RUBIN-OSTER