Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 702 PM EDT Tue Aug 10 2021 Valid 12Z Sat Aug 14 2021 - 12Z Wed Aug 18 2021 ...Heavy rain southeastern Alaska Saturday... ...Overview... Upper pattern remains rather stagnant as features move through the flow, maintaining troughing over the Bering Sea in between upstream and downstream ridging. This will keep an active pattern over the high latitudes into next week with both the northern and southern stream affecting the 49th state. System exiting through the Panhandle Saturday will bring its significant heavy precipitation threat out of the area with a drier few days to follow. The Aleutians and northwestern areas will see a couple systems move through or near the areas with abundant clouds and numerous showers. ...Guidance/Predictability Evaluation... The ensembles remained in good agreement overall with some expected timing/amplitude differences next week over the Bering and near the Aleutians as a couple more systems enter the picture. Overall, a blended solution was preferred. This included the 12Z ECMWF which paired best with the ensembles, followed by the 12Z GFS and part of the Canadian. The UKMET was again farthest from the consensus. The systems south of the Aleutians, containing the remnant moisture of ex-Tropical Storms Lupit and Mirinae, will tend to lift northeastward toward the central/eastern Aleutians and AKPen next week, bringing in some rainfall to the region. Timing differed in the guidance but was within the expected spread for this time range. Again, a middle ground solution showed little change from the forecast 24 hrs ago. ...Weather/Threats Highlights... Some locally heavy rainfall will be possible early Saturday over the Panhandle as the front clears through the area, followed by some showers and then clearing. To the north, deep upper low in the Arctic will allow another 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 next week as the boundary slowly sinks southward and then eastward just ahead of the upper trough. Temperatures will generally be below normal across most of the state, focused on northern areas. Some slow moderation is possible next week but the continued troughing will likely result in only small changes to the pattern, perhaps nearing or above normal temperature across the Aleutians by next Wednesday. Fracasso 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 Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Fri, Aug 13. - Heavy rain across portions of mainland Alaska, Sun-Mon, Aug 15-Aug 16. 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