Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 622 PM EST Tue Jan 04 2022 Valid 12Z Sat Jan 08 2022 - 12Z Wed Jan 12 2022 ...Overview... A blocky and persistent upper upper ridge over northeastern Russia/the Bering Sea should finally weaken some and retreat westward during the medium range period. This will lessen its influence on Alaska and allow for lower mid-upper heights to come into the state, with a busy storm track situated near/south of the Aleutians and the northern Pacific/Gulf of Alaska. This will favor increasing moisture and brisk winds into southern parts of Alaska from the Aleutians into Southcentral Alaska and the Panhandle by the weekend into early next week. ...Guidance Evaluation and Preferences... The latest model guidance, particularly the ensemble means, continue to show good agreement on the overall synoptic scale pattern, but increasing uncertainty in the details. Nearly all of the models agree that a blocky high over northeast Russia should retreat westward by Saturday as an upper low retrogrades westward across the mainland Alaska and into the southeast Bering through Sunday. South of the Aleutians and into the Gulf of Alaska however remains rather chaotic as the models struggle to resolve details surrounding multiple streams/surface lows rotating around a main region of upper level low pressure. Eventually, the mainland system should merge into the broader low south of the Aleutians, creating a persistent plume of moisture directed towards southern Alaska. Model guidance remains incredibly varying with timing, strength, and placement of the surface lows/frontal systems, but with no clear outliers at this time. With decent enough agreement days 4-5, WPC was able to utilize a multi-model deterministic blend. After that, uncertainty increases with various systems and shortwaves, and so a blend more towards the ensemble means seemed the best starting point right now to mitigate these differences. This approach maintained a fairly consistent forecast with yesterdays WPC progs for days 4-7 as well. ...Weather/Hazard Highlights... Increasing moisture is likely by the weekend across south-central Alaska and the Panhandle as a warm front, stemming from low pressure over the northern Pacific, pushes into the Gulf. The frontal system should help direct a persistent plume of deep Pacific moisture towards the region Sunday-Tuesday. There's a pretty decent signal in the guidance for a potentially significant precipitation event, with multiple days of moderate to heavy precipitation from roughly Kodiak Island to much of the Panhandle. A strong pressure gradient setting up between low pressure in the Gulf and High pressure to the north of Alaska will result in very windy conditions, with gusts has high as 60mph possible in some places. Elsewhere across Alaska, the weather should generally be dry, with the exception of a few light showers across higher terrain inland. The Aleutians should also remain rather unsettled and wet through the weekend under the influence of low pressure south of the region. Temperatures across the state should start out chilly and much below normal, especially across western and eastern Alaska where daytime highs could be 20-30 degrees below normal. However, by early next week, temperatures should quickly moderate to above normal across much of the state, except the North Slope region which remains stuck beneath surface high pressure through much of the period. 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 Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Tue, Jan 8-Jan 11. - High winds across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Jan 8-Jan 9. - Much below normal temperatures across portions of mainland Alaska, Fri-Sun, Jan 7-Jan 9. - Much below normal temperatures across portions of mainland Alaska, Fri-Sat, Jan 7-Jan 8. 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