Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 549 PM EDT Wed Aug 14 2024 Valid 12Z Sun Aug 18 2024 - 12Z Thu Aug 22 2024 ***Multiple rounds of heavy rain and strong winds for portions of western Alaska through next Wednesday*** ...General Overview... An amplified and energetic upper level flow pattern across Alaska and the adjacent maritime regions will lead to two separate rounds of impactful weather for the state, with the first over the weekend, and the next into early-middle of next week. The weekend storm is forecast to bring heavy rain and high winds for western portions of the state and extending north across the Brooks Range. After a brief break, the remnants of Typhoon Ampil will likely approach the region toward the middle of next week. Upper level ridging over the Gulf will generally be anchored in place and thus keep weather conditions tranquil for southeastern portions of the state. ...Guidance Evaluation/Preferences... The 12Z guidance overall has stabilized with the deep trough/closed upper low over the southern Bering Sea and the Aleutians for the beginning of the forecast period Sunday, compared to the big model changes noted in earlier model runs. Looking ahead to early next week, ensemble spread is greatest across the Bering Sea region and near the west coast of the mainland as the remnants of Typhoon Ampil enter this region by the Tuesday/Wednesday time period, leading to reduced forecast confidence for the Wednesday-Thursday time period. The guidance agrees the most with the upper level ridge extending northward across the Gulf of Alaska and keeping the storm track away from the Southeast Panhandle region. The ensemble means were gradually increased to about 50% of the overall forecast blend by next Thursday. ...Weather/Hazards Highlights... The incoming Bering Sea low pressure system will bring deteriorating weather conditions across the western mainland as a warm front lifts northward with an increase in rain and wind, likely followed by another surge of wind as the cold front pivots through the region. Moderate to heavy rainfall is expected for portions of the Brooks Range, and extending south across the southwestern mainland and to the Alaska Peninsula as the main moisture plume moves through. Rainfall amounts could reach 1 to 2 inches for some of these areas, with the highest totals likely for western portions of the Brooks Range. Depending on how strong the surface low gets, winds could gust 40-50 mph at times across the terrain and also near the western coast. Looking ahead to next week, the next system (remnants of Typhoon Ampil) are expected to reach the Bering Sea region, and if the remnant low remains organized, another round of impactful rain and wind could affect some of those same areas for Tuesday into Wednesday, including across the Aleutians. Stay tuned as future forecasts refine things further. Temperatures are generally expected to be slightly below average across the northwestern half of the mainland through Wednesday where the main storm track will be, and a gradual warming trend after that. Warmer and generally above average readings will likely be commonplace across the southeastern mainland and extending to the southeast Panhandle region where the upper ridge axis will be governing the overall weather pattern, with pleasant late summer conditions most days. 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