Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 701 PM EDT Tue Apr 11 2023 Valid 12Z Sat Apr 15 2023 - 12Z Wed Apr 19 2023 ...Cold pattern for much of Alaska may start to ease next week... ...Overview... Upper ridging nosing into northeastern Russia will favor continued troughing over mainland Alaska this weekend into next week. This will for the eastern half of an omega block configuration atop a Rex block configuration with a closed low in the subtropics near and just west of the Dateline. The rather stable/stagnant pattern may be interrupted by weaker waves but overall this will promote a dry and cold period for most of the state with lighter precipitation for coastal Southcentral and into the Panhandle. ...Guidance Evaluation/Predictability Assessment... Multi-day ensemble trends have been shown better than average continuity, especially the GEFS mean and ECMWF ensemble mean, and their forecasts formed the majority of the starting point. The 12Z GFS appeared too strong with a shortwave east of Kamchatka into the heart of the upper ridge around next Monday, which generally is not supported nor typical, so this solution was not favored. The 12Z ECMWF may be too strong with incoming vorticity along the east side of the upper ridge across western Alaska next Monday (as it can be), which is seen as another lower probability solution. Both the deterministic and ensemble means of the GFS/ECMWF show a closed low to the northwest of Hawai'i which should act to maintain the amplified, but not over-amplified, pattern into next week before the pattern starts to shift. Given the tendency for models to break down the upper ridge too soon, will continue to favor the ridge maintenance into next week, which is supported by the CPC D+8 progs showing a strong positive height anomaly near the central Aleutians. Storm track will be well removed from the mainland, with an initial Gulf system slowly decaying through the period. Utilized a multi-model/ensemble blend for the starting point, which downplayed the unfavorable aspects in the GFS and ECMWF in what were otherwise reasonable forecasts. ...Weather/Hazard Highlights... Troughing will keep well below normal temperatures in the forecast for especially western but also interior sections of the mainland as high pressure over the Bering this weekend drifts northeastward into the Beaufort Sea. It may take until the middle of next week for any appreciable moderation in temperatures to be realized, though this period will at least be milder than the deep cold in the near term. Initially strong pressure gradient between the Bering high and the Gulf low will favor NW gap winds across the Aleutians into the AKPen which may exceed 40 kts. Precipitation will be mostly confined to the Panhandle, especially Saturday as the weakening occlusions rotates northward around the dying parent low. Fracasso Hazards: - High winds across the eastern portion of the Aleutians to the southern portion of the Alaska Peninsula, Fri-Sun, Apr 14-Apr 16. - Much below normal temperatures across portions of mainland Alaska, Fri-Mon, Apr 14-Apr 17. 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 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