Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Sun Aug 07 2022 Valid 12Z Thu Aug 11 2022 - 12Z Mon Aug 15 2022 ...Cool/wet-to-snowy pattern for August continues across the North while rounds of late week heavy rainfall likely across the South... ...Guidance/Predictability Assessment... There has been a significant change in the forecast guidance since yesterday from the Aleutians southward which has resulted in a rather abrupt shift in the synoptic pattern from late next week onward. An occluded cyclone that was forecast to track south of the Aleutians yesterday is now replaced by a rather solid ridge of high pressure that is forecast to expand from the Pacific into the Bering Sea next weekend. Downstream from the ridge, a nearly stationary cyclonic circulation is now featured over the Gulf of Alaska through much of the medium-range period. This pattern shift is unanimous in all of the major guidance including the ensemble means. Meanwhile, the synoptic pattern pertaining to the northern stream of cold air from the Arctic remains largely unchanged in the forecast guidance. 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. With the pattern change in the guidance since yesterday, much of the threat of heavy rain will be focused along the southern coastal and high terrain sections of Alaska late this week with an occluded low that is forecast to linger in the Gulf but gradually weaken with time. The central portion of Alaska should be sandwiched in between the more active weather in the North and the South, and should expect the least amounts of precipitation. 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 and then filter southward relatively slowly down the west coast by next Monday. 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 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