Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EDT Sun Oct 17 2021 Valid 12Z Thu Oct 21 2021 - 12Z Mon Oct 25 2021 ...Stormy pattern continues into next weekend from the Aleutians to Southern and Southeast Alaska... ... Guidance and Predictability Assessment... Upper level low pressure should remain parked over the Gulf of Alaska through the period as multiple shortwaves dropping through the Aleutians and into the Gulf reinforce the upper pattern. The guidance shows good agreement on the large scale pattern through most of the period but continues to struggle with the details, especially later in the period. Big uncertainties across the board loom, especially regarding triple point low redevelopments in the Gulf, shortwaves crossing south of the Aleutians, and another system making its way into the Bering Sea by the end of the period. WPC relied on a majority blend of the deterministic guidance for the first half of the period, but quickly transitioned to mostly ensemble means by the end to help smooth out the smaller scale, harder to resolve details. Some preference was given towards the ECMWF and the CMC over the GFS given better consistency with the ensemble means. This approach maintained reasonable continuity from yesterdays forecast, as well as with downstream across the CONUS. ...Pattern Overview and Weather/Hazard Highlights... The period starts Thursday with a deep surface low lifting northward into the Gulf and slowly weakening. This should keep unsettled wet weather in the forecast from the southern coast to the Panhandle. Most places should see just scattered light to moderate precipitation, though locally heavy precipitation is likely in some spots, with snow in the higher elevations. Meanwhile, another system should cross the Aleutians on Thursday with widespread precipitation and gusty winds likely to accompany. As the system slides east, a couple of triple point developments should act to reinforce mean low pressure across the Gulf through next weekend. This should maintain generally soggy conditions from southeast Alaska to the Panhandle, with conditions finally starting to improve by early next week as the cold front pushes into western North America. Temperatures from the Aleutians to the Panhandle should be mostly below normal through the period as surface low pressure and upper level troughing becomes established over the region. Into the interior and northern Alaska, periods of upper level ridging should keep daytime highs as much as 10 to 20 degrees above normal into next weekend. Santorelli 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