Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EST Tue Nov 26 2024 Valid 12Z Sat Nov 30 2024 - 12Z Wed Dec 4 2024 ...General Overview... A rather blocky upper level flow pattern is expected to be in place across the Alaska domain for the weekend after Thanksgiving, with a cut-off upper high over eastern Siberia. A well defined upper low pinches off from the broader trough axis situated over northwestern Canada, and then slowly retrogrades southwestward towards the southern Bering around the upper high by Monday. This upper low will likely spur surface cyclogenesis over the Gulf region by the middle of next week. Before that, a separate low pressure system over the Gulf this weekend is likely to bring enhanced onshore flow and rounds of heavy rainfall for the southeast Panhandle region, and a +PNA pattern is expected to be in place across western Canada with an upper ridge axis in place across British Columbia. ...Guidance Evaluation/Preferences... The 12Z model guidance suite features reasonably good synoptic scale agreement across the Alaska domain on Saturday, with good overall clustering with the upper low crossing southwest across Alaska through the weekend. There has been a slight northwestward trend in the guidance with this low compared to the 00Z guidance. The models are also in good agreement with the upper high situated across the western Bering and far eastern Siberia. However, the region with the greatest model differences is across the Gulf region and the timing of multiple shortwave impulses that will affect the southeast portion of the state. Overall, the CMC and to a lesser degree the UKMET showed the greatest amount of deviation from the ensemble means and the operational GFS/ECMWF across that area, although they are more in line with the model consensus elsewhere. Model differences become more widespread and significant going into next Wednesday, and thus the ensemble means accounted for a majority of the model blend by that time. ...Weather/Hazards Highlights... Periods of moderate to heavy rain are expected to make weather headlines across the southeast Panhandle for the first few days of December as a potential atmospheric river event sets up and brings several inches of rainfall across the windward terrain. This may lead to enhanced run-off and rises on area rivers. Elsewhere across the state, the majority of the mainland should remain dry, except for a few snow showers at times across the Alaska Range and points south. Windy conditions are likely for the Alaska Peninsula and the eastern Aleutians on Saturday with a strong pressure gradient in place. Frigid temperatures are expected for much of the Interior and the Brooks Range, with overnight lows dropping into the -20s and even -30s in the normally colder valley locations, and highs only recovering to the -0s and -10s for the upcoming weekend. The good news is a moderating trend is likely to commence going into early next week as the upper ridge axis from western Canada tries to build in, and more of a maritime influence develops across southern Alaska. 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