Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 407 PM EDT Tue Sep 24 2019 Valid 12Z Sat Sep 28 2019 - 12Z Wed Oct 02 2019 Models and ensembles show a reasonably well clustered flow pattern forecast at medium range time scales, bolstering forecast confidence in development of highly amplified flow. The WPC medium range product suite was primarily derived from a composite blend of the latest GFS/ECMWF and GEFS/ECMWF ensemble means, with some trend to weight ensembles more in this blend at longer time frames amid gradually growing uncertainty. This solution maintains excellent WPC continuity as coordinated with local Alaskan WFOs. In this pattern a significant and warming upper-level ridge will build over Alaska as an unsettling longwave trough strongly amplifies upstream over the Bering Sea/North Pacific Ocean. Brisk low level winds will transport lead precipitable water values of 0.75 to 1.25 inches northward into the state, including some tropical moisture associated with former tropical system Tapah. Scattered to widespread precipitation will spread from the Aleutians into southwest/western/interior Alaska later this week and then into southern/southeast Alaska on the western periphery of the slowly eastward shifting ridge early next week as energies work increasingly into the Gulf of Alaska. Schichtel 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 precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon-Tue, Sep 30-Oct 1. - Heavy rain across portions of mainland Alaska, Sun, Sep 29. 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