Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 755 PM EDT Tue Jul 12 2022 Valid 12Z Sat Jul 16 2022 - 12Z Wed Jul 20 2022 ...Heavy rain possible for parts of Southcentral Alaska to the southeastern mainland... ...Overview... A persistent upper low centered well north of Alaska toward the North Pole will slowly sink southwestward early next week and meander northwest of the state toward the Chukchi Sea and northeastern Siberia through midweek. Meanwhile energy/shortwave troughs are expected to round the feature to the south, thus passing over Alaska as they move west to east. The most potent such feature will be an upper low passing near the Aleutians and southern Alaska this weekend into Monday. This should be accompanied by a surface low pressure system as well as heavy rain chances, while meandering and reforming surface fronts may affect the northern tier. ...Guidance/Predictability Assessment... Model guidance agreement remains quite good for the northern upper low, with just some typical differences in placement of its center next week among the deterministic models. To the south along the storm track and more rapidly evolving flow, more model variability is present. The upper low near/over the Aleutians Saturday shows notable timing differences in how fast it tracks eastward across the Alaska Peninsula and into the Gulf of Alaska early next week. ECMWF runs have been persistently fast of consensus, along with the UKMET, while the 12Z CMC was rather slow. The 06Z/12Z GFS runs looked most in line with the GEFS and EC ensemble means, so favored them in the model blend early on. Gradually increased the GEFS/EC ensemble mean proportions to over half by days 7-8, which handled the upper low northwest of Alaska well. The results are very compatible with yesterday's. ...Weather/Hazard Highlights... The southern upper low is expected to push a surface low and frontal system across southern Alaska over the weekend into early next week, and with moisture streaming in this will provide a focus for potentially heavy rainfall for Southcentral Alaska and spreading into far southeastern Alaska Saturday-Monday. Chances for rain will spread into the interior as well, with overall lesser amounts. Additional rounds of precipitation are possible through early-mid next week as well, with rounds of energy aloft. Given the proximity of the northern upper low spilling troughing into the state next week, expect temperatures to be near to below normal in most areas, especially in terms of highs. But low temperatures are also forecast to be below normal into Saturday for the Brooks Range and North Slope, with chilly lows in the 30s, following possible snow in the short range period. These lows should moderate closer to normal by Sunday while cooler than average highs persist, but may drop again somewhat as the week progresses with the encroaching trough. Tate Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sat-Mon, Jul 16-Jul 18. - Much below normal temperatures across portions of mainland Alaska, Fri-Sat, Jul 15-Jul 16. 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