ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 300 PM EDT SAT JUL 23 2016 VALID 12Z WED JUL 27 2016 - 12Z SUN JUL 31 2016 ...HEAVY RAIN POTENTIAL FOR SRN/SERN AK MIDWEEK AND THE INTERIOR MID-LATER NEXT WEEK... ...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER PATTERN HIGHLIGHTS/THREATS... THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A BLEND OF THE COMPATABLE 12 UTC GFS AND 00/12 UTC ECMWF RUNS ALONG WITH 00 UTC NAEFS/ECMWF ENSEMBLES DAY4/WED BEFORE TRANSITIONING DAY5/THU TO JUST THESE ENSEMBLE MEANS THEREAFTER CONSISTENT WITH INCREASING FORECAST SPREAD. THIS SOLUTION MAINTAINS GOOD WPC CONTINUITY. AN AMPLIFIED CLOSED LOW/TROUGH IS EXPECTED TO TRACK NEWD OVER THE GULF OF AK WED/THU IN A PATTERN WITH ABOVE NORMAL PREDICTABILITY AND CONTINUITY. THIS WILL SUPPORT SIGNIFICANT LOWER ATMOSPHERIC LOW/FRONTAL DEVELOPMENT TO PROVIDE FOCUS FOR HEAVY WIND/WAVES AND LEAD/WRAPPED HEAVY RAINFALL WITH MAX POTENTIAL INLAND INTO FAVORED COASTAL TERRAIN OF SRN/SERN AK AS FUELED BY A PRECIPITATBLE WATER PLUME UPWARDS TO 1-1.25". THE SUBSEQUENT SRN TIER SYSTEM ENERGY PATTERN IN THE WAKE OF THIS LOW SEEMS LESS AMPLIFIED/ORGANIZED IN MORE PROGRESSIVE FLOW UNDERNEATH AN INCREASINGLY DOMINANT ARCTIC TO WRN/NRN AK MID-UPPER LEVEL TROUGH. THIS AMPLIFYING NRN STREAM SYSTEM WOULD SUPPORT AN ANOMOLOUSLY WELL DEFINED MID-SUMMER FRONTAL PASSAGE GRADUALLY ACROSS THE INTERIOR. THIS WOULD LEAD TO SOME POTENTIALLY HEAVY CONVECTION/RAINFALL AS FUELED BY DYNAMICS ALOFT AND FAVORABLE SWRLY INFLOW WITH ABOUT 1" PRECIPIATBLE WATER VALUES FROM THE BERING SEA IN ADDITION TO WIDESPREAD UNSETTLED WEATHER/POST-FRONTAL COOLING WED THROUGH NEXT WEEKEND. FORECAST SPREAD WITH THIS SYSTEM HAS DECREASED SOME IN RECENT GUIDANCE TO BOLSTER PREDICTABILITY TO NEAR AVERAGE LEVELS. SCHICHTEL