Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 630 PM EDT Mon Oct 19 2020 Valid 12Z Fri Oct 23 2020 - 12Z Tue Oct 27 2020 ...Heavy rain possible for portions of coastal Southcentral later this week into the weekend... ...Guidance/Predictability Assessment... Model guidance today agrees reasonably well that a robust cyclone engulfing southwestern Alaska, the Aleutians, and the Bering Sea late this week will gradually weaken as low pressure waves on the trailing cold front lift toward southern Alaska and eventually across the Panhandle by the weekend and early next week. Meanwhile, the upper pattern is forecast to trend toward a flatter flow as another system nears the western Aleutians by early next week. The 12Z GFS/ECMWF formed a good cluster with the 12Z GEFS mean and 00Z ECMWF ensemble mean for most of the medium-range period. A blend of these model components yielded a surface pressure pattern quite compatible with yesterday's WPC prognostic charts. By early next week, the next cyclone nearing the western Aleutians now appears to take on a more southern track, which is the main difference from yesterday's forecast. ...Weather/Threats Highlights.. Rainfall around the Aleutians system could be locally heavy from the Alaska Peninsula to the Kodiak especially the southeast-facing areas Thu-Fri before gradually moderating during the weekend. By early next week, low pressure waves lifting northward along the trailing front from the weakening cyclone should deliver periods of heavy precipitation from west to east across southern Alaska into the Panhandle. Models are indicating varying degree of intensities associated with these low pressure waves heading toward the coast. Upper ridging will bring above normal temperatures to much of western coastal Alaska and the Interior, especially over the North Slope, with dry conditions along the Arctic coast. Temperatures may be 10-15 degrees above normal along and north of the Brooks Range, and 5-15 degrees above normal north and west of the Alaska Range. Areas of eastern/southeastern Alaska and especially the Panhandle will see near to below normal temperatures as high pressure (around 1045mb) delivers easterly flow to the region Thu-Sat. Temperatures will moderate just a bit next Sun-Mon across the Panhandle as onshore flow picks up. Kong/Fracasso Hazards: - Heavy precipitation across portions of mainland Alaska and the Aleutians, Thu-Fri, Oct 22-Oct 23. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sun-Mon, Oct 25-Oct 26. - Heavy snow across portions of mainland Alaska, Thu-Fri, Oct 22-Oct 23. - High winds across portions of mainland Alaska and the Aleutians, Thu-Fri, Oct 22-Oct 23. 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