Alaska Extended Forecast Discussion National Weather Service College Park MD 703 PM EDT Wed Aug 20 2025 Valid 12Z Sun 24 Aug 2025 - 12Z Thu 28 Aug 2025 ...Guidance Evaluation/Preferences... WPC noted that the GFS has backed off being the most progressive solution with the recent cycle and the ECMWF was now toward the north/east side of the model cluster. The CMC was also noted being much deeper than other guidance, placing features on the southern side of the cluster. Overall, kept continuity by starting with a multi-model approach. Since there was an uptick in model variances for the latter half of the extended period, the ECMWF/GEFS mean/CMC ensembles were included to reduce the noise. The signal for another shortwave emerging over eastern Russia to bring widespread heavy rain to western/southern parts of the state is growing. This latter feature will need to continue to be monitored as it has potential to pack a punch to the western coastal areas in terms of surge/flooding and points inland with heavy rainfall. ...Weather/Hazards Highlights... Through the extended period a deep, closed low will remain anchored over the Arctic, with ridging to the south weakening the trough over of the Gulf. Shortwave energy will likely rotate through the southern periphery of the Arctic low and kick-off an active period of precipitation across much of the mainland continuing through the weekend. Diffluence ahead of potential phasing between a low emerging off of east Russia and the deep arctic system is expected to bring a substantial plume of moisture to the State late this week. This surge of moisture will likely include some of the remnant moisture associated with TS 18W. Heavy rain will move inland across the Mainland towards the Brooks and Alaska Ranges and surrounding locations this weekend. The trajectory of the heavy rain will become orientated more Southwest-Northeast by the start of the week over much of the Southwest/West-central portions of the state before focusing on portions of the southern Coast/Southwest. Confidence on the impacts to parts of the Kenai Peninsula are low currently since it will be dependent of the direction of the flow. High temperatures will likely remain average across the mainland, while widespread cloud cover will probably keep overnight temps above average. Temperatures across the panhandle will be above average late this week due to persistent troughing in the Gulf sending warm southerly air into the region. Campbell 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