Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 727 PM EDT Thu May 27 2021 Valid 12Z Mon May 31 2021 - 12Z Fri Jun 4 2021 ***Heavy rain likely for portions of southern Alaska*** ...Overview and Guidance Evaluation... The weather pattern from Memorial Day through the first few days of June will be featured with a broad upper level gyre situated over the southern Bering and eastern most Aleutians/northern Gulf, with multiple shortwave perturbations pivoting around it along with associated frontal boundaries. A narrow upper level ridge axis should extend across the Interior and northwest Alaska with a stationary frontal boundary across the north-central portion of the state. In terms of the models, there appears to be better than average deterministic agreement through early Wednesday, mainly owing to the amplified pattern in place. The 12Z CMC is closer to the consensus (but not available in time for the fronts/pressures forecast) compared to the 00Z run. By the end of next week, the 18Z GFS is farther east than the better clustered CMC/ECMWF with the main upper low over the Gulf region. The WPC forecast was primarily derived from a blend of the 12Z ECMWF/GFS/00Z UKMET through Tuesday, and then a slight increase in the ensemble means for Wednesday through Friday. ...Weather/Threats Highlights... The persistent low pressure and onshore flow from the Alaska Peninsula to the southeast panhandle region is expected to produce multiple rounds of moderate to locally heavy rainfall for coastal areas and nearby mountain ranges. Some locations could receive a few inches of rainfall next week, especially across topographically favored areas. Some showers can also be expected across portions of the Interior, mainly for the middle of the week. Temperatures are expected to reach the 60s and low 70s across much of the Interior for highs, and remaining quite chilly north of the Brooks range where highs should remain in the 30s and 40s. 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 Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sun-Tue, May 30 - June 1. 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