Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 558 PM EDT Tue Oct 13 2020 Valid 12Z Sat Oct 17 2020 - 12Z Wed Oct 21 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 model/ensemble families, with the GEFS cluster offset from the ECMWF/ECMWF ensembles, and in turn the Canadian/Canadian ensembles. There was enough overlap of the 12z Canadian with the 00-12z ECMWF and 00z ECMWF Ensemble Mean to blend these solutions days 4-6. With growing differences in timing on Days 7-6, I omitted the 12z Canadian global to avoid depicting a low spread over the large area. So the Days 7-8 forecast was a blend of 00-12z ECMWF and 00z ECMWF Ensemble Mean. The continuing differences with offshore surface systems keeps forecast confidence low in the Aleutians to northern Pacific. ...Weather/Threats Highlights.. With the approach of the upper trough, western Alaska to the upper Aleutians/AK peninsula look to be showery Sat. Residual showers are over coastal southern Ak to the panhandle Sun. Moderate to locally heavy showers are expected. The next significant precip event awaits the development of a cyclone from a north Pacific wave midweek. The 00-12z ECMWF show rain developing in the upper Aleutians/possibly the AK peninsula Tue- 20 Oct- Wed 21 Oct. Initial below temperatures near the Ak/Yukon border late this week retreat and transition so much of Alaska is above normal through the weekend into early 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: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sun-Tue, Oct 18-Oct 20. 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