Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 758 PM EDT Sat Aug 27 2022 Valid 12Z Wed Aug 31 2022 - 12Z Sun Sep 4 2022 ***Heavy rain and flooding a concern for portions of southeast Alaska with multiple atmospheric river events*** ...General Overview... An active weather pattern is expected across the Alaska domain for the middle to end of next week, particularly across the southern mainland and across the southeast panhandle region with an onslaught of Pacific moisture surging inland. A strong storm system is progged to cross the Bering and affect western Alaska by the middle of the week with gusty winds and high seas. Much of the region remains within a broad upper trough by the end of the forecast period, with a broad upper low situated over the northern Gulf. ...Guidance/Predictability Assessment... The 12Z guidance suite remains in above average agreement on the synoptic scale through the end of the week, and thus a multi-deterministic model blend worked well as a starting point. The GFS has trended weaker with the Bering Sea system, and the CMC slightly slower with its arrival. By the end of next weekend, the CMC has less of a signal for a low across the Gulf region, whereas the ensemble means still support the idea of having a broad low pressure system in this region. This maintains good continuity from the previous WPC forecast. ...Sensible Weather and Potential Hazards... An impactful and long duration heavy rainfall event is likely across portions of the southeast Panhandle during this forecast period, with multiple atmospheric rivers impacting the region. There will likely be some lulls during this time period, mainly Wednesday night into early Thursday, with a renewed surge next weekend possible. Anomalous moisture flux oriented nearly orthogonal to the terrain will likely lead to daily 1-2+ inch rainfall maxima for the southern portion of the Panhandle, and weekly totals reaching into the 6-12 inch range are well within the realm of possibility for interior portions of the panhandle bordering British Columbia. This could lead to flooding and enhanced runoff concerns, and this is something that will continued to be closely monitored. Elsewhere across the state, isolated to scattered showers are possible each day, mainly across central and southern portions of the mainland. In terms of temperatures, readings are expected to range from the 50s across western Alaska, and mainly 60s and perhaps some lower 70s for the lower elevations of the Interior. Hamrick 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