Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 731 PM EDT Fri May 21 2021 Valid 12Z Tue May 25 2021 - 12Z Sat May 29 2021 ...Overview and model guidance... The 12Z model guidance suite continues to indicate a broad upper low over the Aleutians/Bering Sea and a downstream ridge over parts of mainland Alaska will be the dominant upper features during this forecast period, but some important specifics vary. One of the uncertainties is the role individual waves emerging from the western Pacific will play, including whether they merge with the mean low over the Aleutians/Bering or remain separate. This pattern will tend to focus episodes of precipitation from the Aleutians into the Alaska Peninsula, and eventually farther east along the southern coast. In terms of model choices, the WPC medium range forecast started with a blend of the 12Z ECMWF/GFS/UKMET for the early-middle part of next week. 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 included 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... Initial low pressure and associated frontal system over the Aleutians/Bering Sea 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 eventually southern coast. Some moisture may extend into parts of the western and southern mainland as well. Fronts/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 Alaska Peninsula to Kenai Peninsula and over favored terrain just north of Bristol Bay. 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 above normal highs with the greatest anomalies over the western part of the state, though some moderation may occur after midweek. Hamrick/Rausch Hazards: No significant hazards are expected over Alaska during this forecast period. 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