Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 352 PM EDT Sat Sep 28 2019 Valid 12Z Wed Oct 02 2019 - 12Z Sun Oct 06 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 through about Friday, the northern/southern stream interaction/orientation has resulted in some mixed deterministic model signals in the interim. By next weekend, ensembles trend out of phase out of Asia into the Bering with the ECMWF ensembles flatter while the GEFS/Canadian members show ridging. North Central Pacific system Wednesday will lift toward the eastern Aleutians/Kodiak around Thursday but likely turn eastward into the southern Gulf. Ensemble spread remains both along and across the preferred track (mostly near the 00Z ECMWF) but a middle of the road approach seemed to fit the upper pattern. At the end of the week, uncertainty increases west of the Dateline with a northern stream system diving southeastward through western/southwestern Alaska and into the Gulf. ECMWF ensembles lift the main low northeastward but all ensembles ultimately showed Gulf redevelopment (triple point development). Further complicating the flow will be the likely extratropical transition of current tropical storm Mitag. JTWC forecast takes this across southern South Korea near the 00Z ECMWF track. Timing of and interaction with a northern stream trough (or multiple troughs) over northeastern Russia will ultimately determine the downstream flow. Though the ECMWF ensembles indicated less interaction/more separation and flatter flow across the Bering, opted to lean more on the GEFS/Canadian ensembles that showed more interaction and downstream ridge response into the Bering given the low predictability area (Siberia) of northern stream flow. Confidence is low in the western portion of the area next weekend. 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 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