Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 541 PM EDT Tue Sep 01 2020 Valid 12Z Sat Sep 05 2020 - 12Z Wed Sep 09 2020 ...Heavy rain possible from Kodiak across Southcentral next week... Amplified pattern across the Pacific into/through North America will be aided by the extratropical transitions of Typhoon Maysak (forecast to move north through N/S Korea tomorrow 9/2) and Tropical Storm Haishen (forecast to also move into the Korean peninsula around 9/6). Models and ensembles continue to show meridional flow into SW Alaska early next week as a well-defined system moves across the Aleutians into the eastern Bering and NW Alaska. The 12Z deterministic models mostly surround the ensemble means (GEFS and ECMWF EPS) through Sunday, and a blended solution worked well to start. GFS runs and the ECMWF were still a but farther east than the Canadian/UKMET with the lead system Sat/Sun toward Kodiak or the AKPEN into Bristol Bay. Ensembles were split but perhaps had a few more members carry a weakening low just east of Kodiak. Regardless, this will dissipate in advance of the more substantial system Sun/Mon that will bring in additional rain/wind to the eastern Aleutians through Southcentral. Locally heavy rain is possible in favored south/southeastward-facing locations. An additional area of at least modest rain will be over the western coastline near the track of the surface low. Milder air will lift northward before being shunted eastward as the cold front slowly advances eastward. By next Mon-Wed, warm front will continue northward as the parent low skirts the west coast toward the Seward Peninsula, eventually translating eastward up and over the upper ridge over the Gulf. Back to the west, models/ensembles show additional troughing digging through the western Bering, but at different latitudes. Split the difference for now as upstream extratropical transition will no doubt play a role in the flow orientation/strength. 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, Sat-Mon, Sep 5-Sep 7. 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