Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 642 PM EDT Thu Aug 12 2021 Valid 12Z Mon Aug 16 2021 - 12Z Fri Aug 20 2021 ...Pattern Overview... A closed upper low will linger in the Arctic/Beaufort through much of next week with systems moving eastward underneath its circulation across northern areas. Additional troughing will reload near the Aleutians into the Gulf to the north of building upper ridging in the mid-latitudes. This keeps a quasi-zonal flow across much of the mainland into the Panhandle with several systems and rainfall episodes. ...Guidance/Predictability Evaluation... The 12 UTC ECMWF/GEFS/NAEFS ensemble means remained in reasonable agreement overall with some expected timing/amplitude differences next week over the Bering and near the Aleutians as a couple less certain systems enter the region. Overall, a blended guidance solution was preferred with the means along with the 12Z ECMWF which paired best with the ensembles and WPC continuity. ...Weather/Threats Highlights... Over northwestern areas, deep upper low in the Arctic will allow a northern stream system out of Russia to push eastward underneath/around its circulation. This will bring in an expanding area of precipitation to the northwestern corner of the state and across the Brooks Range early next week as the boundary slowly sinks southward and then eastward just ahead of the upper trough and with approach of a compact Bering Sea low. Lead systems this weekend containing the remnant moisture of ex-Tropical Storms Lupit and Mirinae, will tend to lift northeastward toward the central/eastern Aleutians and AKPen/Northern Gulf of Alaska into early next week, bringing in some enhanced rainfall to the region. Long fetch moisture pulled northeastward may also favor heavy precipitation downstream through midweek into southern/southeast Alaska as additionally enhanced by terrain. Temperatures will generally be below normal across most of the state, focused on northern areas under the trough. Some slow moderation is possible later next week but the continued troughing will likely result in only small changes to the pattern. Schichtel Hazards: - Heavy rain across portions of mainland Alaska, Mon, Aug 16. - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Aug 17-Aug 18. Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php 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