Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 657 PM EST Sat Nov 25 2023 Valid 12Z Wed Nov 29 2023 - 12Z Sun Dec 03 2023 ...Overview... At the beginning of the medium range period Wednesday, an upper trough axis will be located across the eastern Bering Sea/western Alaska. This troughing is likely to pivot east during the latter part of the week and push out warm upper ridging that has had a hold on the eastern part of the state for a while. A surface low or two in conjunction with the upper trough will help to spread some enhanced precipitation into Southcentral around midweek and into Southeast for the latter part of the workweek. Then, additional energy and troughing stretching eastward from Asia and into the Bering Sea may set up an upper low centered near St. Lawrence Island over the weekend. ...Guidance Evaluation and Preferences... Model guidance on the whole is agreeable in showing a midweek trough with some eastward track while additional troughing stretches eastward across the Bering late week into the weekend. But this pattern is prone to individual shortwaves being the main drivers of the weather, providing forcing for fronts and precipitation--and these small-scale features are quite uncertain in placement and timing, and vary tremendously between models and different runs of each model. Models do show some clustering with a surface low in the Gulf on Wednesday, though the 12Z UKMET did not consolidate this low as well as other guidance, and GFS runs hold onto the low in the Gulf for longer while the ECMWF/CMC erode the low as it tracks inland. Then there is some general agreement for a shortwave to track near the Aleutians and then just south of the state around Wednesday-Friday. But even these features show some notable placement/timing differences, and energy across the Bering Sea and the Mainland shows even less clustering. The main saving grace to the forecast today was that the ensemble means were at least agreeable on the troughy pattern. Thus the WPC forecast used a blend of the 12Z ECMWF/GFS/CMC deterministic runs while also incorporating some GEFS and EC ensemble means early in the period, transitioning to half ensemble means by Day 6 and higher by Days 7-8 given the ample differences in the deterministic models. ...Weather/Hazards Highlights... For midweek, enhanced to possibly locally heavy precipitation is likely across Southcentral Alaska, from the Alaska Peninsula into the Kenai Peninsula and toward Prince William Sound. Most of the precipitation looks to be snow over land. Then as the low pivots and potentially more energy comes into Southeast Alaska, precipitation should spread there for the latter part of the week, with perhaps more variable precipitation types depending on the exact time and place. Lighter precipitation may occur for these southern coastal areas into the weekend. Farther west, rounds of precipitation and possibly some gusty winds are likely over the Aleutians given troughing/shortwaves coming across, with some possibly spreading into the southwestern Mainland. The above average temperatures that have been in place across Alaska look to moderate somewhat in the medium range time frame, consistent with the pattern of upper ridging exiting as it gets replaced by troughing. Through the latter half of the week, high temperatures in the southern half of the state should decrease from around 10F above normal to right around average. Meanwhile the northern half goes from 15-25F above average to more like 5-15F above average, dropping highs temperatures from the teens to single digits. Lows could generally stay above average across most of the state though. Tate 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