Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 238 PM EDT Mon May 20 2019 Valid 12Z Fri May 24 2019 - 12Z Tue May 28 2019 Models showed relatively agreement during the first part of the extended period (Fri-Sat). The consensus is that a low pressure system should approach the Alaska Peninsula during that time frame, moving into the eastern Bering Sea. Given somewhat improved consensus, the forecast during days 4-5 was based on a blend of deterministic solutions including the 00Z ECMWF/12Z GFS. After day 5, ensembles show general agreement on the large scale pattern, with the upper trough gradually slowly sliding east, beginning to break down the northern extent of the upper ridge. Models/ensemble have trended a bit slower with the process of breaking down the ridge, however. Differences become quite significant among deterministic solutions with respect to the details of individual systems traversing the broader mean trough. Thus, trended heavily toward the ECENS/GEFS ensemble means during days 6-8 (Sun-Tue), which supported the idea of another low pressure system crossing the Aleutians during that time frame, as the system farther east reaches southern mainland Alaska bringing a round of increased precipitation coverage/intensity as the system moves inland and weakens. Ryan 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 -Heavy precipitation across portions of the southwest and south central mainland Alaska coast, Thu, May 23. -Heavy precipitation across portions of the southwest and south central mainland Alaska coast, Sat-Mon, May 25-27. 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