Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 754 PM EDT Fri Oct 22 2021 Valid 12Z Tue Oct 26 2021 - 12Z Sat Oct 30 2021 ...Overview and Guidance/Predictability Assessment... Model spread does not appear excessive today near the Alaskan landmass. However, toward the latter part of next week, the ECMWF and GFS are completely out of phase near and west of the Aleutians. The ECMWF and EC mean are more compatible with yesterday's forecasts, as a low pressure system/wave riding through the top of the subtropical high in lower latitudes is forecast to head northeastward toward the Gulf of Alaska next weekend. The CMC mean agrees with the ECMWF solutions in the broad sense. The GFS, on the other hand, keeps a strong high pressure system in place south of the Aleutians when a large low pressure system is forecast to approach the western Aleutians during the latter part of next week--a scenario in stark contradiction to the ECMWF and WPC continuity. Therefore, the WPC medium-range forecast grids for Alaska begin with an even blend of the 12Z GFS & GEFS, the 12Z ECMWF/12Z EC mean, together with smaller contributions from the 12Z CMC/CMC mean. The blend is then quickly weighed toward the ECMWF solutions by Day 5 and then progressively trended toward the EC ensemble mean beyond Day 5, together with relatively small percentages from the GEFS mean and the CMC mean. ...Weather/Hazard Highlights... The medium-range period should begin with a frontal wave developing over the northern portion of the Bering Sea next Tuesday. As the frontal wave tracks eastward, precipitation should increase somewhat from the eastern Aleutians to southwestern mainland Wednesday into early Thursday together with gusty winds. Meanwhile, generally quiet conditions are expected for much of mainland Alaska, with occasional snow showers along the North Slope and the Arctic Coastal Plain. The southern coast and Panhandle should see a modest increase of rain/snow through midweek as a broad cyclonic circulation with surface troughs is forecast to meander over the Gulf of Alaska. Expect above normal temperatures to dominate much of interior Alaska to start the medium-range period next Tuesday. A slow cooling trend is anticipated for the entire area as heights aloft are forecast to slowly decline due to the slow approach of the broad cyclonic circulation over the Gulf. This will lead to progressively colder readings along the southern periphery of mainland Alaska and into the Alaska Panhandle for the medium-range period and into next weekend. Kong Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - No significant hazards are expected over Alaska during this forecast period. 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