Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 703 PM EDT Mon Oct 11 2021 Valid 12Z Fri Oct 15 2021 - 12Z Tue Oct 19 2021 ...Stormy Pattern Continues from the Aleutians through Southern and Southeast Alaska... ... Guidance and Predictability Assessment... The latest models and ensemble guidance over Alaska continues to show above average agreement on the synoptic pattern as multiple low pressure systems moving from the Bering Sea into the Gulf of Alaska continue a stormy pattern. Models exhibit some timing and detail variability, but nothing atypical for these time ranges. The WPC Alaskan medium range product suite used the deterministic models (GFS/ECMWF/UKMET/CMC) blended with the GEFS and ECENS ensemble means. More deterministic weighting was given during the early periods with higher predictability, with more weighting towards the ensembles by the end of the period to smooth out the differences. This approach maintains good continuity with yesterdays WPC forecast. ...Pattern Overview and Weather/Hazard Highlights... An energetic and progressive flow aloft will support multiple surface low pressure systems affecting portions of Alaska late this week and into early next week. The first low will be moving into the Gulf by the beginning of the period, offering a continued favorable moisture and enhanced precipitation pattern for southern and southeast Alaska. Moderate to locally heavy rainfall is possible across portions of the Panhandle region, with snow likely in the higher elevations of southern Alaska. Upstream flow is then expected to drive a deep storm into the Bering Sea by next weekend with downstream energy transfer allowing for triple point low developments which should work across the eastern/central Aleutians and the AKPen region and eventually into the Gulf of Alaska by next Monday. This should again bring a coastal and maritime threat for heavy rainfall and gusty winds to the Aleutians this weekend and the southern coast/Alaskan Panhandle by early next week. There remains some differences in exact placement of this low as it gets into the Gulf, which of course would impact precipitation amounts along the coast and also how far inland the precipitation shield extends. Mean low pressure and cloudy/unsettled conditions across the Gulf and southern Alaska region through the period should keep temperatures below normal. Across northern and central Alaska, temperatures should be closer to normal with a period of slightly above normal temps by early next week as weak upper level ridging builds in from the east. 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 Hazards: - High winds across portions of mainland Alaska and the Aleutians, Sat-Sun, Oct 16-Oct 17. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon, Oct 18. 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