Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 745 PM EDT Mon Aug 07 2023 Valid 12Z Fri Aug 11 2023 - 12Z Tue Aug 15 2023 ...Synoptic Overview and Guidance Evaluation/Preferences... The upper level pattern over Alaska during the extended range (Friday-Tuesday) looks pretty stagnant with a deep upper low meandering over the Bering Sea and a somewhat blocky upper ridge across Northern Alaska and into northwest Canada. The main uncertainties in the forecast resides with the details of individual shortwaves/systems rounding the base of the trough towards the Aleutians and southern Coast. The strongest of these systems should move in to the southern Coast this weekend, bringing a threat for gusty winds and heavy rainfall to much of southeast Alaska. On the large scale, models show good agreement on this overall pattern, but do offer some differences in exact placement of the upper low and the systems in the Gulf. Noted the UKMET was faster/farther north and east with the strong system in the Gulf early period and was not included in the blend for today. The WPC forecast used an equal blend of the ECMWF, GFS, and CMC for days 4-6. By late period, the ECMWF was displaced farther west with the low in the Bering. The GFS and CMC showed better consistency with the ensemble means, and so the late period blend used almost equal weighting of the GFS and CMC with the ECENS and GEFS ensemble means. This maintained good continuity with yesterdays forecast as well. ...Weather/Hazards Highlights... The high latitude upper ridge over the northeastern mainland into the Yukon will continue to support above normal temperatures, but trending cooler than what is expected in the short range forecast period. Daytime highs may reach near 80 Friday-Saturday over the Yukon Flats, while the North Slope could see readings rise into the 60s to near 70 mainly away from the coast. By Sunday, temperatures should moderate back closer to normal as upper troughing moves into the region and breaks down the ridge. In terms of precipitation, onshore flow ahead of shortwaves into the Gulf will support rounds of moderate to occasionally heavy rainfall across much of southern Alaska and the Peninsula. The heaviest rain, with 2-4 inches possible, is expected across southeast Alaska/the Panhandle this weekend. Depending on strength of the weekend storm, gusty winds could be an issue for the maritime and coastal areas as well. Santorelli 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 - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sat, Aug 12. 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