Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Mon Aug 08 2022 Valid 12Z Fri Aug 12 2022 - 12Z Tue Aug 16 2022 ...Cool/wet-to-snowy pattern for August returns this weekend across the North while rounds of late week heavy rainfall likely across the South... ...Guidance/Predictability Assessment... Following yesterday's major shifts in the guidance from the Aleutians southward for this coming weekend, things appear to have settled into this new forecast regime. This new regime calls for a solid ridge of high pressure to dominate areas from the Aleutians southward into the Pacific from weekend into early next week. Downstream from the ridge, an occluded cyclonic will be slow to migrate from the eastern Aleutians late this week into the Gulf of Alaska this weekend. Deterministic solutions begin to diverge from the weekend onward. Ensemble means on the other hand are in fairly good agreement for the high pressure ridge to stay put to the south of the Aleutians while the Gulf of Alaskan low loops toward the south. Meanwhile, the synoptic pattern pertaining to the polar vortex remains mostly unchanged in the forecast guidance. Both the deterministic and ensemble guidance indicate an intrusion of polar air into the North Slope by this weekend, followed by a gradual retreat of the cold air by early next week with the ensemble means. The WPC forecast package for Alaska was based on 40% from the 12Z GEFS/06Z & 12Z GFS, 40% from the 12Z ECMWF/00Z or 12Z EC mean, and 20% from the 12Z CMC/CMC mean, transitioning to mostly a consensus of the ensemble means by Day 7. ...Sensible Weather... After a brief warm up late this week, much cooler air from the Arctic is forecast to filter across the North by this weekend with high-elevation snow possible over the Brooks Range. Meanwhile, the greatest threat of heavy rain will be focused along the coastal sections and nearby high terrain of southern Alaska late this week with the passage of an occluded cyclone. In addition, gale force winds with gusts to storm force are possible across the eastern Aleutians on Friday on the back side of this cyclone. This cyclone is forecast to linger in the Gulf but gradually weaken with time. The Panhandle should see a period of enhanced precipitation moving in early next week. Meanwhile, the central portion of Alaska should be sandwiched between a polar front across the North and the heavy rain near the southern coast, with minimal rain chances. Some of the moisture from the southern coast is forecast to penetrate and move across the interior Southeast early next week. Temperatures should recover closer to normal by Friday but cool air from the Arctic will once again bring chilly conditions into the North Slope by the weekend with snowfall possible over the Brooks Range. The polar air is forecast to show limited southward penetration down the west coast and should remain across the North Slope into early next week. Kong Hazards: - Heavy rain across portions of mainland Alaska, Thu-Fri, Aug 11-Aug 12. 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