Alaska Extended Forecast Discussion National Weather Service College Park MD 653 PM EDT Thu Aug 7 2025 Valid 12Z Mon 11 Aug 2025 - 12Z Fri 15 Aug 2025 ...Flooding concerns could linger in Southeast Alaska early next week... ...Overview... Into early next week, the upper trough over the Mainland this weekend will be lifting northeast out of the state. Heavy precipitation may linger across Southeast Alaska from an atmospheric river and energies along the base of the trough, before the trough fully moves away and causes a drying trend. An upper ridge (aside from a Kodiak Island/Kenai Peninsula vicinity shortwave Tuesday) is forecast to cross Alaska behind this first trough and lead to warming temperatures. Meanwhile farther west, longwave troughing will be present across the Bering Sea, with its mean axis slowly shifting east toward the western Mainland through the week, albeit with model differences with embedded shortwaves and surface low pressure/frontal systems. This pattern should lead to increasing chances of generally moderate precipitation moving from the Aleutians early next week, into the western and central Mainland midweek, and reaching the eastern Mainland and Panhandle into late week. ...Guidance Evaluation/Preferences... This weekend's Mainland upper trough will lift northeastward into early next week, but models continue to show variability on the timing. After multiple days of the GFS being the slowest to lift the trough away from the state, recent GFS runs are now among the fastest. The 12Z ECMWF and CMC and the AIFS linger a weak closed low atop central Alaska into Monday. This was a notable change for the ECMWF, whose 00Z run showed faster trough ejection more like the GFS. Given the spread in the operational models and AI/ML models, tried to reach an intermediate solution on the trough's timing. An upper ridge is reasonably well forecast to move across the state behind this first trough. There is surprisingly good agreement (for the extended range) in the 12Z ECMWF/GFS/CMC with a shortwave moving northeast toward the Alaska Peninsula/Kodiak Island vicinity Tuesday to be able to depict this feature and a resulting frontal system in this forecast. Further changes are still possible though. Behind these features, models show broad troughing in the Bering Sea, but with more differences in the details as a couple of rounds of energy are likely to track east from Japan and the Kamchatka Peninsula within the trough. Models may be converging somewhat on a shortwave and surface low to reach the Y-K Delta Wednesday, but show spread in its movement beyond that, and upstream shortwaves also have ample spread. The WPC forecast used a multi-model blend early in the period. As the forecast progressed, quickly ramped up the proportion of GEFS and EC ensemble means to half Day 7 and more Day 8 as spread with the individual models continued to increase. ...Weather/Hazards Highlights... The primary hazard of concern early next week will be heavy rainfall across Southeast Alaska (Panhandle) that may last into Sunday, though heavier rain totals are expected on Saturday (now fully in the short range period). The tail end of a moderate to strong AR could remain in place, so continue to denote a Heavy Rain area for Sunday on the Day 3-7 Hazards map across Southeast Alaska. Southern parts of the Panhandle are likely to see the heaviest rain, but areas farther north could be more sensitive to heavy rain, especially areas near the Mendenhall Glacier that could see a worsening of potential glacial outburst flooding. Lighter showers are forecast by Tuesday-Wednesday in the Panhandle. More moderate precipitation could also linger in the eastern Mainland early next week. Behind this first trough, a shortwave could spread some light to moderate precipitation to the Alaska Peninsula/Kodiak Island/Kenai Peninsula Monday-Tuesday. On the broader scale, incoming moisture ahead of the Bering Sea trough and a surface low pressure system should promote increasing precipitation chances from west to east across the state next week. Rain totals may reach an inch or more over the Aleutians early in the week, and winds could be around 30-35 knots in parts of the Aleutians and Bering Sea depending on the depth of the surface low. By Tuesday and Wednesday generally moderate precipitation will reach the western Mainland, spreading across the central Mainland for midweek and eastward into later week. Precipitation is expected to be mostly rain, but higher elevations of the Brooks and Alaska Ranges could see some snow. Temperatures should start next week cooler than average under the upper trough. But as the pattern transitions to mean upper ridging, near to above normal temperatures are likely across much of the Mainland. Highs are forecast to be generally in the 60s with some 70s. Tate 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