Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 720 PM EDT Wed Sep 16 2020 Valid 12Z Sun Sep 20 2020 - 12Z Thu Sep 24 2020 ...Overview and Guidance/Predictability Assessment... The extended period begins with a surface low and associated cold front pass through the southern Mainland/panhandle into Canada while a low over the Pacific/Bering deepens as it advances toward the Aleutian Chain. While there is some timing and strength differences, this system is forecast to be well-defined and wrapped up as it tracks toward/over the Aleutians mid-to-late in the forecast period. Stronger winds and additional focused rain will accompany this system. High winds may impact parts of Kodiak Island and Kenai Peninsula Monday and Tuesday, as well as, heavy precipitation spanning from Unimak Island to Anchorage and the surrounding area. The area of heavy precipitation will shift east along the southern coastal area to Glacier Bay, with heavy rain across the Southeast Tuesday and Wednesday. There continues to be some spread in the timing of the low pressure system that tracks across the Aleutians during the mid/late period; however to a lesser degree than yesterday. Persistence favored a combination of the 12Z ECWMF/GFS/CMC for most periods with increasing weighting of the 00Z EC ensemble and 12Z GEFS mean by Tuesday and Wednesday. ...Weather/Threats Highlights... Lingering clouds and showers are possible across parts of the southern Mainland and panhandle as a front moves into Canada early in the period. Increased cloudiness, heavy precipitation and increasing gusty winds will accompany a fairly progressive low pressure system as it tracks across the Bering, the Aleutians and into the Gulf of Alaska next week. Much of the southern coastal areas and the North Slope will have maximum daily temperatures near or below average through at least mid week, while much of the Interior will observe above average temperatures. 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 mainland Alaska, Mon-Tue, Sep 21-Sep 22. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Sep 22-Sep 23. - Heavy rain across portions of the Alaska Panhandle, Tue-Wed, Sep 22-Sep 23. - High winds across portions of mainland Alaska, Mon-Tue, Sep 21-Sep 22. - High winds across portions of the Alaska Panhandle, Tue, Sep 22. 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