Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 629 PM EST Sun Nov 26 2023 Valid 12Z Thu Nov 30 2023 - 12Z Mon Dec 04 2023 ...Overview... At the beginning of the medium range period Thursday, a relatively narrow upper trough axis will extend northwest to southeast from around St. Lawrence Island across the southwestern Mainland and into the Gulf of 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 lingering precipitation to Southcentral and pushing into Southeast for the latter part of the workweek. Then, additional energy and troughing stretching eastward from Asia and across the Bering Sea is forecast to stretch across much of the state by next weekend and may set up an upper low centered near St. Lawrence Island. Embedded energies and surface low pressure/frontal systems are much less certain, but there is some general consensus that low pressure should set up again in the Gulf early next week and enhance precipitation for Southeast Alaska. ...Guidance Evaluation and Preferences... Model guidance on the whole is agreeable in showing a narrow trough Thursday with some eastward track late week 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 lingering in the Gulf at the start of the period Thursday, and some general agreement for a shortwave to track near the Aleutians and then just south of the state around Thursday-Friday. But even these features show some placement/timing differences, and energy across the Bering Sea and the Mainland shows even less clustering. The northern Pacific is also a trouble spot by the weekend, though with a general trend toward surface and upper lows in the northern Pacific/Gulf by early next week. The main saving grace to the forecast again 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/UKMET deterministic runs early in the period, gradually transitioning to over half ensemble means Days 7-8 given the ample differences in the deterministic models. ...Weather/Hazards Highlights... Some precipitation should linger into Thursday across Southcentral Alaska, with enhanced amounts possible in favored areas of the Kenai Peninsula and toward Prince William Sound. Most of the precipitation looks be snow over land. Windy conditions may be possible into Thursday near Cook Inlet between Kodiak Island and the Kenai Peninsula if winds funnel in a tight pressure gradient pattern. Southeast Alaska should also see some precipitation for the latter part of the week, with perhaps more variable precipitation types depending on the exact time and place. Amounts in today's forecast have trended down somewhat though. Lighter precipitation may occur for these southern coastal areas into the weekend, with a possible but uncertain ramp-up especially over Southeast by early next week. Farther west, rounds of precipitation and possibly 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 part 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 high 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