Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 318 PM EDT Wed Sep 25 2019 Valid 12Z Sun Sep 29 2019 - 12Z Thu Oct 03 2019 Latest models and ensembles still show an amplified medium range flow pattern, but forecast spread with weather focusing systems embedded within the larger scale flow has increased days 4-8, lowering forecast confidence closer to average. The WPC medium range product suite was primarily derived from a composite blend of the 12 UTC GFS/UKMET and 12 UTC GEFS/00 UTC ECMWF ensemble means days 4/5, strongly trending blend weightings toward ensembles at longer time frames amid growing uncertainty. The 00 UTC ECMWF in contrast offered outlier surface system progressions compared to the 12 UTC GFS/UKMET and was discounted. The newer 12 UTC ECMWF has since trended more in line with the aforementioned preferred model and ensemble blend. This overall solution maintains good 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 rain across portions of the Alaska Panhandle and mainland Alaska, Sun-Tue, Sep 29-Oct 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