Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 659 PM EST Wed Jan 22 2025 Valid 12Z Sun Jan 26 2025 - 12Z Thu Jan 30 2025 ...Heavy precipitation shifting from the southern coast this weekend into the Panhandle early next week... ...Heavy snow from the Alaska Range across interior western and central Alaska to eastern Brooks Range through the weekend and possibly into Monday... ...Trending much colder next week... ...Overview with Guidance Evaluation and Preferences... A low pressure system that is forecast to track from southwest to northeast through mainland Alaska will be the main focus of impactful weather during the first half of the medium-range period. Guidance today continues to exhibit quite a bit of variability regarding the speed of motion as well as the cross-track location of the system's center. Of note is the GFS's shift toward the eastern track envelop in recent runs, compared with the Canadian model which has shifted to the far left side of the envelop in recent runs, while the ECMWF continues to take a track in between those extremes but with considerable run-to-run variability on the forward speed of the system. The uncertainty shown by these model outputs would have significant implications on the eventual placement of a band of overrunning snow forecast to develop and intensify to the west of a frontal boundary over interior Alaska as the system center approaches from the southwest. By midweek, guidance generally splits the system into two parts--one continues to track northeast toward the northern periphery of the Canadian Arctic Archipelago while the other part weakens over the Gulf of Alaska. The EC mean, nevertheless, favors digging a deeper 500mb trough south across western Alaska into the Gulf of Alaska before lifting northeast through midweek. There is another 500mb trough coming from the north coast of Siberia attempting to interact with the digging trough as well. The placement of the trough axis shows rather good agreement among the EC, GEFS, and CMC ensemble means though, along with good run-to-run consistency. The WPC medium-range forecasts were derived based on 40% from the 12Z ECMWF and 00Z/12Z EC mean, 40% from the 12Z GFS/GEFS, and 20% from the CMC/CMC mean with high percentages from the ensemble means from Day 6 onward. This blend yield a solution very compatible with WPC continuity. ...Weather/Hazards Highlights... A persistent long fetch of moisture across mainland Alaska will be further enhanced this weekend as a low pressure system approaches from the southwest. The increasing interaction between the cyclone and a preexisting front across mainland Alaska will generate bands of heavy snow from the Alaska Range across interior western and central Alaska and into the eastern portion of Brooks Range through the weekend and possibly into Monday. High winds on Saturday over northern and eastern Alaska are expected to weaken by Sunday but the winds could strength again on Monday when the cyclone traverses mainland Alaska from southwest to northeast. Meanwhile, a period of heavy precipitation should initially focus along the southern coast and then gradually push more into the Panhandle by early next week. The Days 3-7 Hazards Outlook depicts the above weather threats. Toward midweek the majority of the mainland should trend drier while some precipitation may linger over the Panhandle, with specifics determined by upper trough/surface details. Farther west, there is emerging potential for a Bering Sea wave to bring a period of brisk winds and light to moderate precipitation to the Aleutians and possibly some of the Alaska Peninsula early-mid week. The forecast pattern transition will bring a pronounced colder trend. Central/eastern parts of the mainland will be particularly warm versus normal during the weekend with some plus 20-30F or greater anomalies. The approach and arrival of upper troughing from the west will bring steadily colder temperatures, with nearly the entire state seeing below to well below normal readings by midweek. The North Slope and southern Panhandle could hold onto slightly above normal anomalies into early Wednesday. Kong/Rausch 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