Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 555 PM EDT Wed Oct 14 2020 Valid 12Z Sun Oct 18 2020 - 12Z Thu Oct 22 2020 ...Guidance/Predictability Assessment... The models indicate the upper trough moves slowly east from the Bering Sea and to the west coast of Alaska over the weekend, reloading in the Bering Sea next week. The models are in good agreement into the weekend over northern to central Alaska, with differences developing centered over the northern Pacific and the adjacent Aleutians. The timing and phasing of individual waves varies by models/ model runs, with the 12z GFS initially in good agreement with other models/meas through about day 4.5, and then the GFS holds on to the anticyclone in southern AK longer than other solutions, and is slower in moving the storm north towards the Aleutians. The cross check with the GEFS Mean show the operational GFS to be an outlier, with the 500 mb pattern in the GEFS more closely resembling the Canadian and ECMWF Ensemble means Mon and Tue 20 Oct. Manual progs blended the 00-12z ECMWF and 00z ECMWF Ensemble Mean,as the 12z Canadian cyclone track was offset to the west in the north Pacific to the Aleutians days 6-7. Better agreement develops by day 8 as the occluded low moves more slowly in the southern Bering Sea. The next shortwave 500 mb trough rotating south of this cyclone across the north Pacific should spawn the next cyclone development in the middle to latter portions of next week. ...Weather/Threats Highlights.. With the approach of the upper trough, western Alaska to the upper Aleutians/AK peninsula/Kodiak Island look to be showery Sat-Sun. The next significant precip event awaits the arrival of the north Pacific wave midweek in the Aleutians. The 00-12z ECMWF show rain becoming widespread in the upper Aleutians/possibly the AK peninsula Tue- 20 Oct- Wed 21 Oct. Locally heavy rain is possible. Initial below temperatures near the Ak/Yukon border late this week persist into early next week. Much of western Alaska is above normal through the weekend into the middle of next week. Petersen 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: None forecast. 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