Alaska Extended Forecast Discussion National Weather Service College Park MD 620 PM EDT Thu Aug 14 2025 Valid 12Z Mon 18 Aug 2025 - 12Z Fri 22 Aug 2025 ...Guidance Evaluation/Preferences... 12 UTC GFS/ECMWF/UKMET/Canadian model solutions seem reasonably well clustered valid for Monday into early Wednesday in a lingering blocky pattern with above normal predictability. A composite seems to provide a solid forecast basis that maintains good WPC product continuity and has good multi-model ensemble support. The broad blend process of compatible guidance also tends to mitigate lingering smaller scale systems variances as consistent with individual predictability. Later, the 12 UTC GFS seems to work disloging energies too quickly into/underneath an anchoring closed upper low/trough over the Arctic Ocean mid-later next week compared to most other guidance. Considering longevity aspects of this pattern, prefer a 12 UTC ECMWF/Canadian and overall compatible 12 UTC GEFS/ECMWF/Canadian ensemble mean heavy blend increasingly over time that offers slower flow transition. The newer 18 UTC GFS has trended back more in line with the blend. ...Weather/Hazards Highlights... The medium range upper flow pattern over Alaska should remain highlighted well into next week by a slow to dislodge closed low/trough over the Arctic Ocean and an eastern Gulf of Alaska closed upper low/trough that resets over the western Gulf into next mid-late week with infusion of system energy associated with current central Pacific invest 99W. This system will first spread unsettled/wet weather over the Aleutians/vicinity early next week. An initially deepened surface low pressure system set to slowly eject from the eastern Gulf early-mid next week will keep periodic rain chances over the Southeast Panhandle and up into eastern SouthCentral, with the most appreciable rainfall lingering into early this period over the southern Panhandle with closest main low proximity and rotating easterly wave energies. Across the North Slope/Brooks Range down into the Interior, shortwaves offer multi-day periodic enhancement of rain and Brooks Range focusing heavier snow chances with rotation through the base of a deep low anchored well north of the area over the Arctic Ocean. There is also with time expected emergence of an upstream flow transition as a less series of shortwaves and associated surface systems/rain chances work northeastward to the Bering Sea that by later next week offers potential to bring enhanced rains/winds downstream into/across the western Mainland. Schichtel 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