Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 551 PM EDT Mon Sep 14 2020 Valid 12Z Fri Sep 18 2020 - 12Z Tue Sep 22 2020 ...Overview and Guidance/Predictability Assessment... Upper troughing will linger along 160-170W into next week, favoring a progressive yet rather vigorous pattern. Lead system on Friday will lift northeastward on strong southwesterly flow into Canada. Models still waver on evolution into southwestern areas on Thursday, but a deterministic consensus blend sufficed among the 12Z GFS/ECMWF/Canadian/UKMET. Next system should dive through the Bering, across the Aleutians, and find its way to the Gulf late Sat into Sun. Maintained a deterministic preference of the GFS/ECMWF/Canadian as the ensembles still lose this system due to the spread and weak pressure gradient. Finally, last system out of the NW Pacific showed rather good agreement for the lead time between the 12Z GFS/ECMWF/Canadian and 00Z ECMWF ensemble mean (12Z GEFS mean continued to favor another system farther south). Trend has been deeper with this system and by next Tue (day 8) all the guidance points to a well-defined wrapped-up system southwest of Kodiak. Did increase ensemble weighting to tone down the deeper deterministic solutions as agreement at day 8 does not mean as much as shorter lead times. To the north, consensus approach sufficed with weaker troughing through the period in between anomaly centers. Discounted any model with seemingly spuriously defined features. ...Weather/Threats Highlights... Showery patter in the wake of the first system for the weekend across southern coastal areas, but some enhancement may be possible. More focused rainfall may return with the third system next Sun-Tue over the Aleutians to the AKPEN by the end of the period. Max temperatures will be near to above normal over the Interior but generally near to below normal over southern coastal areas into the Panhandle as well as for the North Slope. 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 precipitation across portions of mainland Alaska, Thu-Fri, Sep 17-Sep 18. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu-Sat, Sep 17-Sep 19. - Heavy rain across portions of the Alaska Panhandle, Sat-Sun, Sep 19-Sep 20. - High winds across portions of southern coastal Alaska, Thu-Fri, Sep 17-Sep 18. 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