Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Tue Aug 22 2023 Valid 12Z Sat Aug 26 2023 - 12Z Wed Aug 30 2023 ...Heavy rain likely this weekend along the southern coastline as wet pattern lingers into next week for southern Alaska... ...Overview... Wet weather associated with a lingering front across northern Alaska this weekend is forecast to give way to drier conditions by early next week. Meanwhile, a heavy rain event appears in store for the southern coastal areas of Alaska through this weekend. The heavy rain threat should lessen by early next week but the associated wet pattern is forecast to linger, keeping the weather unsettled across southern Alaska into midweek next week. ...Guidance Evaluation/Preferences... Models generally depict a longwave upper trough will remain the dominant feature to the west and southwest of Alaska while a strong upper ridge axis will tend to remain in place just to the east. Multiple shortwaves rounding the longwave trough will tend to merge as they move toward southwestern Alaska ahead of the strong ridge axis. Most of the guidance holds the ridge in place through the medium-range period. The exception is the 12Z ECMWF which begins to dig a trough into western Alaska early next week, eventually eroding the strong ridge to the east. This scenario is not supported by both the 00Z and 12Z EC ensemble means as well as the rest of the guidance. Thus, today's WPC forecasts for Alaska for Days 6-8 were based mainly on a blend of the 12Z GEFS, 00Z/12Z EC mean, 12Z CMC mean, which maintains a ridge pattern to the east of Alaska, as a large scale occluded low slides eastward into the Aleutians through the first half of next week. ...Weather/Hazards Highlights... Initial surface waves and lingering front across northern Alaska with light to moderate rainfall will give way to drier conditions by early next week. To the South, a heavy rain event appears in store for the southern coastal areas of Alaska through this weekend as a strong jet ahead of an occluded low over the Bering Sea pumps copious Pacific moisture into the region. The heavy rain threat should lessen by early next week but the associated wet pattern is forecast to linger, keeping the weather unsettled across southern Alaska into midweek next week. A large scale cyclone sliding east across the Aleutians will keep unsettled weather across the island chain into midweek. In terms of temperatures, the eastern interior and southern Panhandle will see the best potential for above normal highs, while other areas should be near to below normal. The coolest anomalies are likely to be over the Brooks Range to North Slope to the north of a front, though the coastal communities may stay closer to average. Low temperatures look to be more above normal until early next week, though with the possible exceptions of the Seward Peninsula and northwestern Mainland. 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: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Aug 26-Aug 27. 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