Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Tue Sep 22 2020 Valid 12Z Sat Sep 26 2020 - 12Z Wed Sep 30 2020 ...Overview and Guidance/Predictability Assessment... One upper low rotating south of the region will drive a surface low into the Gulf and northward towards the southern coast next weekend into early next week. There will be another upper-level low that will drop through the Bering Strait on Friday that will help establish a mean trough over the region by early next week. By the tail-end of the extended period a deepening surface low and associated frontal system will approach to the south of the western Aleutians. Run-to-run consistency has improved somewhat, especially for the first couple of days. The preferred blend for this forecast was varying weights of 12Z CMC/ECWMF/GFS with light amounts of the ECWMF/GEFS ensemble means. While there is increasing spread in timing and placement with the low near the Aleutians/Gulf by the end of the forecast, utilizing the means wash out some of the strength/details with this system- particularly the surface winds. This low will likely have gale-force winds associated with it, therefore, using more of the deterministic for the latter half of the extended helped maintain at least small-craft wind speeds. Winds will be an element of concern going forward with future forecasts. ...Weather/Threats Highlights... Parts of the southern coastal areas may have heavy rain associated with a surface low entering the Gulf of Alaska and hanging around for a few days. There may be a mix of snow, particularly in the higher elevations. As the low weakens so does the coverage of precipitation. However, another low is expected to lift northward through the Gulf which may result in locally moderate to heavy precipitation by early/mid-week across the Southeast and parts of the southern Mainland. The western Aleutians will have increasingly unsettled and rainy conditions by early next week as another low pressure system approaches. With mean troughing in place over much of the state, daily temperatures will largely be near or below normal for late September. Campbell 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, Tue, Sep 29. 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