Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 745 PM EDT Wed Oct 12 2022 Valid 12Z Sun Oct 16 2022 - 12Z Thu Oct 20 2022 ...A very stormy pattern continues for much of Alaska and adjoining waters to include a major prolonged heavy precipitation and flooding threat next week for South-central to Southeast Alaska... ...Overview and Guidance/Predictability Assessment and Weather/Hazards Highlights... The 12 UTC GFS/ECMWF/UKMET and Canadian solutions seem well clustered into Sunday/Monday and are well supported by ensembles, bolstering forecast confidence. In this period, lingering low energies will keep the Bering Sea and Western/Southwestern Alaska into the Interior unsettled with some periods of wintry precipitation and some gusty winds. Deep low/frontal genesis downstream over the western to northern Gulf of Alaska and long moisture fetch lead inflow will combine with topograhic lift enhancement in support a pattern with enhanced maritime to coastal winds/waves and a multi-day heavy rainfall/runoff and elevation snowfall threats across South-central and Southeast Alaska. There is only a small break before guidance develops and tracks another deep low pressure system to work from the west Pacific back into the Gulf of Alaska by Tuesday in what is proving to be quite an astonding series of storms so far in October in a highly energetic pattern. However, forecast spread increases with the details/timing of this potent storm and an uncertain partial connection to moisture associated with current Tropical Depression 21 over the southwest Pacific. Accordingly, increasingly added into forecast equation more run to run consistent 12 UTC GEFS/ECMWF ensemble mean guidance, but made manual enhancements to the composite model and ensemble blend to ensure development of a deep system with stormy seas/gale winds and a renewed threat for heavy rain/runoff and elevation snowfall threats back into South-central and Southeast Alaska into next Wednesday. Meanwhile, there is also a growing guidance signal for yet another major and large low to flourish and bring widespread high winds/waves across the Bering Sea through the Aleutians into the north Pacific along with wrapping heavy rains Tuesday into next Thursday. This system would also then threaten much of West/Southwest Alaska and underneath through a stormy Gulf of Alaska and inland with wrapping inflow into South-central then Southeast Alaska yet again by next Wednesday/Thursday with downstream potent energy transition and system progression. Schichtel Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Wed, Oct 15-Oct 19. - High winds across portions of the Alaska Panhandle and mainland Alaska, Tue, Oct 18. 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