Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 746 PM EDT Wed Jul 13 2022 Valid 12Z Sun Jul 17 2022 - 12Z Thu Jul 21 2022 ...Heavy rain possible for parts of Southcentral Alaska to the southeastern mainland and western Panhandle... ...Overview... A persistent and anomalously deep (for this time of year) upper low will be in place just north of eastern Siberia and meander toward the Chukchi Sea through next week, spreading a general troughing pattern across the bulk of Alaska along with cool temperatures. An energetic shortwave trough stemming from the upper low but separating somewhat is forecast to track west to east across the Alaska Peninsula and quickly across the southern mainland early next week, pushing a surface low pressure system through those areas with chances for heavy rain. Additional rounds of energy south of the low and meandering and reforming surface fronts affecting the northern tier will keep a cool and wet pattern in place over the state through much of next week. ...Guidance/Predictability Assessment... Model guidance agreement remains fairly good for the northern upper low, with just some typical differences in placement of its center next week among the deterministic models. The operational ECMWF in particular shows the center of the low moving farther southeast than other guidance even by Monday, while the EC mean is a bit farther southeast compared to other ensemble means, but not to the same extent as the deterministic EC. To the south along the storm track, model variability also remains with the timing details of the trough/low passing over the Alaska Peninsula eastward early in the week, with the EC and UKMET still among the faster solutions, but models have converged somewhat. The WPC forecast blend favored the GFS runs as a good middle ground through the forecast period, with some components of the ECMWF/CMC/UKMET early, and phasing the ECMWF and UKMET out in favor of the EC ensemble mean for the latter part of the period, for a nod toward the farther southeast solutions but less extreme than the deterministic EC. ...Weather/Hazard Highlights... The southern upper low is expected to push a surface low and frontal system across southern Alaska 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 and toward the western Panhandle Sunday-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 and frontal systems in place that could focus the moisture. There is a chance of Southcentral Alaska seeing enhanced rain amounts again around midweek. Precipitation may be in the form of snow in northwestern and north-central Alaska, especially in higher elevations. Given the proximity of the northern upper low spilling troughing into the state next week, expect temperatures to be well below normal in most areas, especially in terms of highs. Low temperatures could be around average on Sunday but are forecast to cool again Monday-Thursday for the northern two-thirds of the state, starting in the northwest and spreading inland as the trough encroaches. Chilly lows in the 30s are possible for parts of the Brooks Range and North Slope. Tate Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Jul 16-Jul 17. - Heavy rain across portions of mainland Alaska, Sun, Jul 17. - Much below normal temperatures across portions of mainland Alaska, Sat, Jul 16. - Much below normal temperatures across portions of mainland Alaska, Mon-Tue, Jul 18-Jul 19. 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