Alaska Extended Forecast Discussion National Weather Service College Park MD 750 PM EDT Sun Sep 21 2025 Valid 12Z Thu 25 Sep 2025 - 12Z Mon 29 Sep 2025 ***Unsettled weather pattern continues for southern and southeast Alaska with multiple rounds of rain and mountain snow*** ...General Overview... The organized low pressure system that will be crossing the Bering Sea and Aleutians is expected to reach the northern Gulf by Thursday, with strong onshore flow and enhanced rain and mountain snow from the Kenai Peninsula to southeast Alaska to close out the work week. An amplified shortwave dropping southeastward from eastern Siberia is likely to cross the southwestern mainland and re-energize the existing Gulf low for the weekend. A third system may approach the Aleutians going into Sunday and Monday, and an arctic trough is likely to persist for the northern third of the state as well. ...Guidance Evaluation/Preferences... The 12Z guidance suite features higher than normal model spread for a day 4 forecast on Thursday, especially dealing with the shortwave and potential closed low developing over eastern Siberia and diving rapidly southward to the northern Gulf. The UKMET is most amplified with this scenario, whereas the AIFS guidance is weaker and more in line with the ensemble means through Friday. The CMC also differs from the consensus by having a weaker solution with an incoming shortwave trough south of the Alaska Peninsula for the end of the week. Model spread becomes quite pronounced by Sunday, and the CMC likely differs the most by this time with a large surface high just south of the Aleutians, whereas the other guidance strongly favors an incoming storm system from the western Bering. Given the increased uncertainty in the deterministic guidance, more reliance was placed on the ensemble means for this forecast package, accounting for about 2/3rds of the blend by next Monday. ...Weather/Hazards Highlights... The next low pressure system will bring the likelihood for more unsettled weather for southern coastal areas of Alaska towards the end of this week. High winds are expected along the Aleutians on Wednesday as the system strengthens over the Bering Sea. The low could bring widespread moderate to heavy rain to South-Central and Southeast Alaska on Thursday into Friday. In terms of temperatures, colder conditions will be commonplace across most of the mainland, with subfreezing overnight lows becoming more widespread across the Interior, and 10s to low 20s near the Brooks Range. There may be a renewed surge of colder conditions by next Saturday over northwestern Alaska depending on how the low near eastern Siberia evolves, and changes to the forecast are likely. Hamrick 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