Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 543 PM EST Sat Feb 15 2025 Valid 12Z Wed Feb 19 2025 - 12Z Sun Feb 23 2025 ...Overview... A parade of shortwaves and surface lows rounding the base of a broad trough/upper low over the Aleutians will continue to bring an active/wet pattern to coastal portions of Alaska, particularly the Southern Coast and into the Southeast/Panhandle. The upper low may weaken with time, with the core of it gradually shifting northward into the Bering Sea. Meanwhile, upper ridging will persist over much of the Mainland, bringing a period of much above normal temperatures across the state. ...Guidance Evaluation and Preferences... There continues to be general agreement on the large scale pattern described above, but a lot of variability and uncertainty with individual lows and shortwaves into the Southern Coast and Panhandle. This lends to a very low confidence forecast in the specifics, including track and intensity of any given low. There is some general agreement though that one surface low should lift towards the Southern Coast on Thursday, with another one tracking into the Gulf next weekend. This generally sets up a pattern of persistent onshore flow into Southeast Alaska. The 12z GFS and ECMWF seemed most agreeable on this setup, and were most consistent with the ensemble means. The UKMET was more aplified early period, showing more ridging across the Aleutians and Bering Sea and was not used at all for todays WPC forecast progs. The CMC was reasonable clustered with the GFS and ECMWF early period, but did become faster with a couple of shortwaves towards the Panhandle later in the period. The WPC forecast today was based on a non-UKMET blend early in the period, with significant weighting towards the deterministic guidance. After Day 5, gradually increased the ensemble mean contribution to 60 percent of the blend by Day 8, with the other 40 percent comprised of the GFS and ECMWF. This helped maintain some level of definition to individual systems, which the ensemble means tended to wash out much more. ...Weather/Hazards Highlights... A heavy rain threat will be ongoing across the Kenai Peninsula/Prince William Sound and vicinity by mid next week, as a surface low lifts towards the region and a cold front directs moisture towards the coast. Heavy rainfall is possible along the immediate coast, but heavy snow is possible in the higher terrain. The threat should wane some later in the weak, but remain wet. The focus then shifts towards the Southeast/Panhandle region as ample moisture is directed into this region leading to multiple days of moderate to possibly heavy rain into next weekend. Otherwise, the Alaska Peninsula to Aleutians should be generally wet and unsettled underneath of the parent upper low. A weak front through the interior portions of the state may bring some light showers to some places. Upper ridging persisting through the period will keep temperatures well above normal through the period, with some locations across southwest and southern Alaska possible to see daytime highs 20 to 30 degrees above normal. The North Slope region may start out below normal, but should also trend warmer with time. Santorelli 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