Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 336 PM EDT Fri Sep 27 2019 Valid 12Z Tue Oct 01 2019 - 12Z Sat Oct 05 2019 Amplified yet progressive upper pattern will trend toward renewed troughing in the Gulf of Alaska by next weekend. While the longwave pattern remains generally predictable, the northern/southern stream interaction/orientation has resulted in some mixed deterministic model signals. Overall a blend of the 00Z ECMWF with the 06Z GEFS mean and 00Z ECMWF ensemble mean offered a good starting point through the period. Recent GFS runs were not necessarily outside the spread, but were just not preferred based on the better agreement of the ECMWF to the ensemble means. Lead system of interest will be in the Gulf on Tuesday with locally heavy rain and mountain snow for Southcentral coastal areas into the Panhandle. Next system will lift out of the central North Pacific toward the eastern Aleutians before turning eastward into the southern Gulf. 00Z ECMWF nicely split the difference between the farther north Canadian and south GFSs Thu-Fri. At the end of the week, uncertainty increases west of the Dateline with a possible northern stream system diving southeastward into the Gulf, but did not fully embrace the 00Z ECMWF as it showed southern stream development in previous cycles though resulting in a similar forecast by next Saturday. With the likely extratropical transition of current TD 19W (forecast to be a typhoon as it recurves through Japan) adding addition uncertainty into the picture, ensemble mean consensus seemed prudent. This yielded reloaded troughing into the Gulf downstream of building Bering ridging. 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 Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Mon-Tue, Sep 30-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