Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 755 PM EDT Thu Aug 25 2022 Valid 12Z Mon Aug 29 2022 - 12Z Fri Sep 2 2022 ***Heavy rain and flooding becoming more likely for portions of southeast Alaska next week with multiple atmospheric river events*** ...General Overview... An active weather pattern is expected across the Alaska domain for next week with a deep upper low situated over the Gulf for early in the week, and then a strong storm system is progged to cross the Bering and affect western Alaska by the middle of the week. Much of the region remains within a broad upper trough by the end of the forecast period, with upper ridging across central/western Alaska tending to keep the trough in place for longer than usual. ...Guidance/Predictability Assessment... The 12Z GFS/ECMWF/CMC/UKMET solutions are in above average synoptic scale agreement for much of the extended forecast period, and a multi-deterministic blend sufficed as a starting point in the forecast process. The latest 12Z ECENS trended to the northwest and closer to the model consensus for the Bering Sea low compared to its prior run, and improving forecast confidence. By the end of the week, the CMC starts becoming more out of phase across the Aleutians and Bering, so less weighting was given to it by days 7 and 8, and more towards the ensemble means for that time period. ...Sensible Weather and Potential Hazards... A highly impactful heavy rainfall event is likely across portions of the southeast Panhandle region with multiple atmospheric rivers impacting the region. Anomalous moisture flux oriented nearly orthogonal to the terrain will likely lead to daily 2-4 inch rainfall maxima for the southern portion of the Panhandle, and weekly totals well into the 6-12 inch range are well within the realm of possibility. This could lead to serious flooding issues, and something that will continued to be closely monitored. Elsewhere across the state, isolated to scattered showers are possible each day as the overall weather pattern remains unsettled. In terms of temperatures, readings are likely to be below average for most areas with highs generally in the 50s for western Alaska, and 60s for east-central Alaska, and lows mainly in the 40s south of the Brooks range. Hamrick Hazards: - Heavy rain across portions of the Alaska Panhandle and southern mainland Alaska, Sun-Thurs, Aug 28-Sept 1. 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