Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 256 PM EDT Tue Sep 10 2019 Valid 12Z Sat Sep 14 2019 - 12Z Wed Sep 18 2019 Progressive and wavy upper pattern will tend to slow down next week in response to an upstream deep trough nearing the Sakhalin Oblast (north of Hokkaido). This favors ridging just west of the Dateline and troughing along 160W by the end of the period. In between, a modest system will traverse the Bering Sea this weekend and push into western Alaska Sun/Mon before its triple point low decays in the Gulf. Attendant frontal boundary may slow and stall along 50N as the flow becomes more southwesterly rather than westerly as heights buckle. Global models/ensembles showed a better clustering of solutions today vs 24 hrs ago. 12Z GFS was a bit quicker than all other models and most ensembles, so used the 06Z GFS in part with the 00Z ECMWF to even out the quicker/slower forecasts, respectively, vs the means. Trended toward a majority ensemble weighting by next week Tue/Wed due to increased uncertainty in northern stream flow across the North Slope (weakness may drift westward as troughing settles into 160W) as well as southern stream (Pacific) uncertainty in any wave development along the front. Pattern will be fairly wet for southwestern/western areas through Southcentral as the front comes through. Upper trough will continue with lighter rainfall. Panhandle will see a brief break in between departing system Saturday and next system late Monday. Multi-day rainfall totals may exceed several inches (4-5") from eastern Kenai to Yakutat with less rainfall farther inland. Fracasso 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 rain across portions of the Alaska Panhandle and mainland Alaska, Fri, Sep 13. 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