Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 639 PM EDT Wed Oct 4 2023 Valid 12Z Sun Oct 8 2023 - 12Z Thu Oct 12 2023 ***Atmospheric River event expected this weekend and into Monday across the southeast Panhandle*** ...Overview... A rather active weather pattern will likely be in place for the weekend with a couple of organized Gulf low pressure systems affecting the southeast Panhandle region. Several inches of rainfall from atmospheric river events is expected, and this could 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. An even stronger storm system will be possible across the Bering Sea region towards the middle of next week. ...Guidance Evaluation and Preferences... The 12Z model guidance suite generally indicates near average forecast spread through the weekend and into the first half 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 Monday with seemingly average predictability and continuity. With greater mesoscale differences becoming apparent by the middle of next week, use of the ensemble means increased to about 50%. The intensity of the Gulf low and the low approaching the Bering late in the forecast period was increased slightly from the forecast blend. ...Weather and Hazards Highlights... There will likely be an atmospheric river going into the weekend across portions of 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 the Chugach Mountains. This low pressure system will likely have gale to storm force winds associated with it for the coastal waters. The highest precipitation totals will likely be over the Southeast Panhandle, where 2-4 inch rainfall totals are likely, and perhaps higher for some of the coastal ranges. Between low pressure east of the Alaska Peninsula and high pressure forecast over the North Slope, a broad area of the mainland to the eastern Bering Sea should have a fairly tight pressure gradient supportive of brisk to strong winds and gaps winds. Looking ahead to Wednesday and especially Thursday, a strong low pressure system is looking more likely to develop, and if this comes to pass, strong winds and heavy rainfall for the Aleutians would be a concern. Hamrick Hazards: - Heavy rain across portions of Southeast Alaska, Sat-Mon, Oct 7-Oct 9. 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