Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 604 PM EDT Fri Aug 13 2021 Valid 12Z Tue Aug 17 2021 - 12Z Sat Aug 21 2021 ...Overview... It remains generally the case that a closed upper low will linger in the Arctic Ocean 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 enhanced rainfall episodes. ...Guidance/Predictability Evaluation... 12 UTC GFS/ECMWF solutions now seem better clustered, fit well with WPC continuity and overall sit near the middle of the full envelope of model and ensemble solutions days 4-6 (Tue-Thu). Favor bringing into the composite increasing amounts of compatible but less detailed GEFS/NAEFS/ECMWF ensemble means into days 7/8 to address growing forecast spread as predictability lowers from above to near normal. ...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-Fri, Aug 17-Aug 20. 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