Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 323 PM EDT Sun May 19 2019 Valid 12Z Thu May 23 2019 - 12Z Mon May 27 2019 Models have come into somewhat better agreement during the first part of the extended period. The consensus has trended toward the idea of keeping a relatively strong upper ridge in place across the Gulf of Alaska, and keeping a broad upper trough farther west across the Aleutians/North Pacific for longer. Thus, expect one weakening low pressure system to be crossing the eastern Bering Sea/Alaska Peninsula on Thu, with another system following about 1-2 days behind it, approaching the eastern Aleutians/Alaska Peninsula by Fri-Sat. Given somewhat improved consensus, the forecast during days 4-5 was based on a multi-model deterministic blend including the 00Z ECMWF/CMC and 06Z GFS. After day 5, ensembles show general agreement on the large scale pattern, with the upper trough gradually sliding east and breaking down the northern extent of the upper ridge. Differences become quite significant, however, with respect to the details of individual systems traversing the broader mean trough. Thus, trended heavily toward the ECENS/NAEFS ensemble means during days 6-8 (Sat-Mon), which supported the idea of another low pressure system crossing the western/central Aleutians during that time frame, as the system farther east reaches southern mainland Alaska and weakens in the anticyclonic flow on the northern periphery of the upper ridge. 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 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