Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 624 PM EDT Wed Oct 21 2020 Valid 12Z Sun Oct 25 2020 - 12Z Thu Oct 29 2020 ...Heavy precipitation possible for the Panhandle and coastal Southcentral areas late weekend/early next week... ...Guidance/Predictability Assessment... Troughing is forecast to settle and be reinforced over Southcentral next week as upper ridging south of the Gulf moves very slowly eastward. Additional ridging over the central Pacific will flatten and allow quickly-moving systems into the mean trough axis along 160W. This setup will maintain a wet southwesterly flow into the Panhandle and portions of coastal southeastern Southcentral (Kenai eastward) as the surface boundary may be blocked from moving east by the upper ridge. The 12Z models were in general agreement on the synoptic scale but varied on system timing/track/intensity within the longwave pattern. Ensemble means also differed but were within tolerance. The 12Z GFS was quite different with the handling of a surface wave toward Kodiak vs the ECMWF/Canadian (west vs east), which did not fit the consensus nor continuity. Opted to rely mostly on the 12Z ECMWF/ECMWF ensemble mean with some added details of the Canadian despite its offset system timing. By later in the week, nearly zonal flow east of the Dateline suggest low confidence in details but this should keep the storm track south of the Aleutians regardless. To the north, height falls will usher in colder temperatures for the North Slope and much of the Interior north of the Alaska Range. This cold front may make its way toward Denali and Southcentral but should weaken as its support moves into Canada. ...Weather/Threats Highlights.. Expect the heaviest precipitation during the period to be over the far southern/southeastern mainland and Panhandle as a series of frontal waves move through the Gulf and into the Panhandle or southeast mainland. Several inches of rainfall (perhaps several feet of snow at higher elevations) are probable, with localized areas of focused activity. Lingering surface/upper low in the Bering will promote showery weather early in the period before a drier trend develops. Above to much above normal temperatures should prevail over a majority of the mainland during the period, especially north of the Alaska Range. The North Slope and western portions of the mainland should see the greatest positive anomalies ahead of the upper trough/cold front dropping into the state from the northwest late Monday. This will bring temperatures back toward more seasonable levels but still above normal over the North Slope. The Panhandle and parts of the far southeastern mainland are likely to see below normal readings through the period. Fracasso Hazards: - Heavy precipitation across portions of the Alaska Panhandle and coastal Southcentral Alaska, Sun-Mon, Oct 25-Oct 26. 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