Alaska Extended Forecast Discussion National Weather Service College Park MD 632 PM EDT Sun Aug 17 2025 Valid 12Z Thu 21 Aug 2025 - 12Z Mon 25 Aug 2025 ...Guidance Evaluation/Preferences... The 12z guidance is in relatively good agreement that troughing will persist over northern portions of the mainland and the Arctic through next weekend, while troughing in the Gulf eventually moves inland over the panhandle by next weekend. Troughing in eastern Russia/Bering Sea late this week may phase with the Arctic low so there's some divergence in the guidance on how to resolve that. The Canadian and European deterministic models clustered well with each other through the medium range period. On days 4 (Thursday) and 5, a general model blend, including the UKMET with heavy weighting to the EC and CMC, were used. On day 5, the GFS begins to catch up to the EC/CMC trough in the Bering, while agreeing with them elsewhere in the domain. By day 6, the Canadian/Euro ensembles and GEFS are introduced to the domain. GFS/EC are more progressive with an upper low over Chukchi Sea, while EC/CMC are more progressive than GFS over eastern Russia/Bering. The GFS is removed from the blend on day 7 due to the much more progressive low in the Gulf/Panhandle as well as over Beaufort Sea. The EC/CMC and their respective ensemble means tend to capture the diffluent pattern from the Bering to the mainland fairly well on days 7 and 8. ...Weather/Hazards Highlights... The synoptic pattern across the Alaska region on Thursday will feature ridging over the Bering Sea, a deep Arctic low, that will likely persist through the rest of the week, and a closed upper low in the Gulf. Shortwave energy is likely to rotate through the southern periphery of the Arctic low and kick-off an active period of precipitation across much of the mainland beginning Wednesday and 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. Heavy rain is possible across portions of the west coast into interior areas next weekend. 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. Kebede 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