Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 722 PM EDT Mon Jun 17 2024 Valid 12Z Fri Jun 21 2024 - 12Z Tue Jun 25 2024 ...Overview and Guidance Evaluation/Preferences... Most of mainland Alaska will be situated under a narrow upper level ridge axis extending from northwestern Canada going into the end of the week. A compact upper level polar is forecast to slowly drift across western Siberia, with gradual weakening going into next weekend. Meanwhile, the main storm track across the North Pacific is expected to feature two low pressure systems, with the lead system approaching the southeast Panhandle going into Saturday, and the second one passing south of the Alaska Peninsula Sunday/Monday, with periods of showers for the coastal areas, and scattered thundershowers for the Interior. The 12Z model guidance, along with the 18Z GFS, are in great overall agreement across the Alaska domain to start the forecast period Friday, with a general deterministic model blend sufficing as a good starting point for fronts and pressures, and mainly a GFS/ECMWF blend for QPF with some previous WPC continuity and ensemble biased corrected QPF. Going into the weekend, there are some minor placement differences with the polar low over eastern Siberia and the weaker upper low/surface low near the central Aleutians, and the best agreement resides across the eastern Gulf with the storm system approaching the Southeast Panhandle region. Model differences grow quite a bit going into next Monday/Tuesday across the North Pacific, and also across the northern half of the mainland as a potential second polar low drifts south. The 18Z GFS better fits the consensus compared to the 12Z run, which had a strong low pressure system over the Aleutians/southern Bering which was not supported by the model consensus nor the ML guidance. The ensemble means accounted for about half of the forecast blend going into early next week. ...Weather/Hazards Highlights... Isolated to scattered showers/storms can be expected most days across the Interior during the afternoons and early evenings, with the best prospects for more widespread coverage on Friday and again next Monday. A more organized round of rain is forecast for the southeast Panhandle going into Saturday, although it's not expected to be a major event with most areas getting under an inch of QPF. Areas north of the Brooks Range should generally remain dry with the Arctic high exerting its influence across the North Slope and Arctic Coast. In terms of temperatures, afternoon highs are expected to reach well into the 70s for many areas across the Interior, perhaps reaching 80 degrees for the Yukon Flats, and also just north of the Alaska Range. Overnight lows here should also be rather mild with readings bottoming out from the upper 40s to upper 50s. The Arctic Coast will likely remain chilly with onshore flow from the Arctic Ocean, with highs generally from the middle 30s to middle 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