Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 348 PM EDT Mon Sep 16 2019 Valid 12Z Fri Sep 20 2019 - 12Z Tue Sep 24 2019 The guidance continues to show an active northern Pacific stream which features two dominant storm systems tracking along or just south of the Aleutians and then into the Gulf of Alaska. These systems will likely bring some enhanced rainfall to the Aleutians/Alaskan Peninsula and support much heavier precipitation at times over the southeastern coast/Panhandle. Model and ensembles continue to highlight the southeastern coast/Panhandle region for the highest five-day precip totals (on the order of 5+ inches). Meanwhile, an upper low (with one or more individual impulses) should meander somewhere between the northwestern mainland coast and eastern Siberia which would support below normal temperatures by this weekend and potential for rain/snow mix across the North Slope/interior Alaska, with snow possible in the higher terrain. Models show good agreement on the first system tracking from the Peninsula to the Southern Coast Friday-Saturday and eventually weakening over southeast AK on Sunday. The second system should move along or just south of the Aleutians Saturday-Sunday, and into the Gulf on Sunday. There remains some disagreement on timing with this system, with the GFS/GEFS suite a bit slower than the ECMWF/ECENS. The 00z CMC sat somewhere in the middle of the two. Across Northern AK, there is fairly good synoptic agreement on a meandering upper low, with normal detail/timing differences arising later in the period. Across the board, the WPC forecast uses a blend of the 12z GFS/00z ECMWF/00z CMC for days 4-5, with increasing ensemble mean contributions days 6-8. This results in a good middle ground solution for the second Aleutians/Gulf low and fairly modest changes/refinements versus continuity. Santorelli 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, Fri-Sat, Sep 20-Sep 21. 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