Alaska Extended Forecast Discussion National Weather Service College Park MD 741 PM EDT Mon Aug 18 2025 Valid 12Z Fri 22 Aug 2025 - 12Z Tue 26 Aug 2025 ...Guidance Evaluation/Preferences... Non GFS guidance were in good agreement on the overall synoptic pattern late this week into early this weekend, when variance increases. The 12z GFS was notably more progressive than the EC and CMC with a deep and phasing trough over east Russia/the Bering Sea. The GFS also has more pieces of shortwave energy rotating around the base of the Arctic low. Days 4 and 5 consisted of a general model blend consisting of the 12z EC/GFS/CMC/UKMET with greater weighting on the EC and CMC. The upper low in the East Pac in the GFS is notably farther south than the EC/CMC solutions, which clustered well together. Ensemble means were integrated into the blend on day 6 and increased in weighting through day 8. The Canadian and GFS signal another shortwave emerging over E. Russia on days 7/8. ...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