Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EST Wed Nov 22 2023 Valid 12Z Sun Nov 26 2023 - 12Z Thu Nov 30 2023 ...Synoptic Overview... An upper ridge axis is expected to extend from British Columbia to the northern Alaska mainland for this upcoming weekend, along with a weakening trough over the Alaska Peninsula and across the Gulf waters. It appears the ridge will try to remain in place across much of the eastern Interior going into the early to middle portions of next week, and thus keeping temperatures generally above average. The opposite will hold true across the western Bering where a broad upper level gyre is expected to reside through early in the week, before gradually moving eastward towards the western coast and weakening, following by another broad upper low vortex across the Bering by next Thursday. Meanwhile, a storm system will likely develop in the general vicinity of the Alaska Peninsula sometime around midweek and bring a renewed round of organized precipitation. ...Guidance Evaluation and Preferences... The 12Z model guidance suite features good overall synoptic scale agreement to begin the forecast period on Sunday, so an equal portion of the UKMET/ECMWF/GFS/CMC was used as a starting point in the forecast process for this time. Going forward to Tuesday, timing differences become apparent with shortwave perturbations crossing south of the Aleutians, with the main difference being a more zonal flow pattern depicted in the CMC that loses support from the other guidance going into the middle of the week, so the CMC was not incorporated beyond Tuesday. The GFS becomes stronger with the low pressure system developing over the Gulf region by late in the period, but still reasonably close to the ECMWF (the CMC is out of phase with a ridge axis across the Gulf by this time). Numerous model differences exist across the Bering Sea and Aleutians by next Thursday, and this is where forecast confidence is lowest. Ensemble means were gradually increased to about 50% of the forecast blend by Days 7 and 8. ...Weather/Hazards Highlights... The weather pattern will continue to remain active across southern coastal portions of the state Sunday into Monday, particularly from the Kenai Peninsula eastward to the northern portion of the southeast panhandle region, where sustained onshore flow will advect copious moisture inland and produce locally heavy coastal rain and mountain snow. There may be some abatement on Tuesday ahead of the next round of precipitation from the Alaska Peninsula to Prince William Sound for mid-week. Most of the Interior should be dry this weekend, but some snow showers are likely for southern and central portions of the state going into early in the week owing to warm air advection aloft. Strong winds are also likely for portions of the Seward Peninsula on Sunday with a strong pressure gradient across the eastern Bering. In terms of temperatures, highs are generally expected to be in the 20s to lower 30s for most inland areas, and 10s for the North Slope and lower-middle 40s for the southern coastal areas.es going south into the 20s/30s/40s. Hamrick 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