Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 700 PM EDT Sat May 22 2021 Valid 12Z Wed May 26 2021 - 12Z Sun May 30 2021 ...Overview and model guidance... The overall weather pattern will generally feature a large scale upper low that will slowly move from the southern Bering Sea to the eastern Aleutians region during the medium range period. Multiple shortwave perturbations and surface lows are expected to pivot around this main upper low and produce episodes of rainfall for southern Alaska. Meanwhile, an upper level ridge axis should extend from southeast to northwest across mainland Alaska, and an Arctic trough should pass over northeast Alaska and northwest Canada. In terms of model choices, the WPC medium range forecast started with a blend of the 12Z ECMWF/GFS/UKMET for the Wednesday-Thursday time period. Similar to yesterday, the CMC differed more from the ensemble means along with greater timing differences, so it was not favored for this forecast cycle. Beyond that time, the forecast trended to include more of both the ECENS and GEFS mean to account for timing differences with individual shortwaves and amplitude. Some previous WPC continuity was also included. ...Weather/Threats Highlights... The initial low pressure center and associated frontal system over the Bering Sea and central Aleutians, as well as one or more trailing systems that may merge into the overall mean low, should bring periods of unsettled weather to areas from the Aleutians through at least the Alaska Peninsula, and then portions of the mainland southern coast. Fronts and embedded waves may provide localized enhancement of precipitation and winds at times. The best signal for highest totals during the five-day period exists from the eastern Aleutians to the Kenai Peninsula, with some areas likely to receive an inch or more of rainfall. In terms of temperatures, the Panhandle and portions of the southern mainland as well as parts of the North Slope will tend to see slightly below normal high temperatures during the period. Other locations will likely experience near to above normal highs with the upper ridge in place. Hamrick Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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