Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 651 PM EDT Fri Sep 04 2020 Valid 12Z Tue Sep 08 2020 - 12Z Sat Sep 12 2020 ...Stormy conditions should gradually subside by the middle of next week; extratropical Haishen may reach the western Aleutians by next weekend... Windy and rainy conditions associated with an occluded cyclone should still be the main story early next week especially for western Alaska. Conditions will slowly improve by the middle of next week as the cyclone weakens into a trough along the Brooks Range. Considerable clouds and scattered areas of rain will linger over mainland Alaska into the latter part of next week with cool afternoons and milder than normal nights. The best chance of heavy rain will be on the southern periphery of the state, from the Alaska Peninsula on Labor Day, shifting east toward the northern Panhandle by Tuesday into Wednesday. Toward the end of next week, there was a significant shift in the forecasts led by the 00Z EC mean from the Aleutians westward. The GEFS and Canadian means have not responded to this change yet but the 12Z GFS and 12Z ECMWF agree fairly well to abandon the idea of having a cyclone approaching the central Aleutians from the southwest by next weekend. The reason for this pattern shift appears to be due to more energy is given to the extratropical amplification of Super Typhoon Haishen currently south of Japan which will then absorb the low that is forecast to drift into the western Aleutians by the middle of next week. This pattern shift does not appear to impact the forecast all that much for mainland Alaska, however. The WPC Day 4-8 Alaskan prognostic charts were based on a blend of the 00Z EC mean, 12Z ECMWF, 12Z GFS and the 12Z GEFS with more emphasis toward an even blend of the 12Z GFS and ECMWF for Days 7 and 8. Kong Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy rain across portions of mainland Alaska, Mon, Sep 7. - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Sep 8-Sep 9. - High winds across portions of mainland Alaska, Mon-Tue, Sep 7-Sep 8. WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html