Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 757 PM EDT Tue Oct 3 2023 Valid 12Z Sat Oct 7 2023 - 12Z Wed Oct 11 2023 ...Multi-day heavy precipitation threat from southern to Southeast Alaska along with windy conditions and freezing rain and snow potential for Southwest Alaska and the Alaska Range into the Interior... ...Overview... A rather active weather pattern will likely be in place for the end of the week and going into the weekend with a couple of organized Gulf low pressure systems affecting the southern coastal areas, principally from the Kenai Peninsula eastward to especially include the southeast Panhandle region. Several inches of rainfall from atmospheric river events is expected, and result in enhanced run-off and elevated stream flows. Temperatures are expected to drop steadily going into the weekend and beyond with generally below normal readings for much of the mainland. ...Guidance Evaluation and Preferences... The 12Z model guidance suite generally indicates near average forecast spread through the weekend and the beginning of next week. A general deterministic blend of the 12Z GFS/ECMWF/CMC and some UKMET and previous WPC continuity seems to offer a good forecast starting point through Sunday with seemingly average predictability and continuity. With greater mesoscale differences becoming apparent by next Monday and Tuesday, use of the ensemble means increased to about 50%. ...Weather and Hazards Highlights... There will likely be a strong surge of lower latitude moisture/atmospheric river later this week into the weekend across southeast Alaska as a warm front lifts north across the Gulf of Alaska in advance of a developing Gulf system. This moisture should produce heavy rainfall and mountain snows from the Panhandle back to portions of the southern mainland coast. Details for additional potential systems reaching the Gulf of Alaska become more uncertain over the weekend into next week, but there is a growing signal for a subsequent deep low approaching from the northeastern Pacific into early next week as a maritime threat and as a focus for onshore flow and additional rain. Confidence decreases with respect to precipitation coverage and amounts, but the overall pattern seems to offer a continued potential for enhanced rainfall and mountain snows extending across the broad southern mainland tier, including south-central and the Alaska Range as well as the Panhandle region. Lingering cold temperatures may pose a threat for impactful freezing rain into Southwest Alaska for the Lower Kuskokwim and vicinity, and across the southern Interior including the Copper River Basin, with snow over other areas. For the five-day period, the highest precipitation totals will likely be over the Southeast. Between low pressure east of the Alaska Peninsula and high pressure forecast over or north of the North Slope, a broad area of the mainland into the eastern Bering Sea should have a fairly tight gradient supportive of brisk to strong winds and gaps winds to monitor. Hamrick Hazards: - Heavy rain across portions of Southeast Alaska, Fri-Sat, Oct 6-Oct 7. 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