Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 740 PM EDT Sat Sep 04 2021 Valid 12Z Wed Sep 08 2021 - 12Z Sun Sep 12 2021 ...Pattern Overview and Model Guidance... The latest suite of model and ensemble guidance continues to show very good agreement on the overall large scale synoptic pattern through much of the Alaska extended range period which features a broad upper level low which should drift south and eastward into the Bering Sea by the latter part of next week. This should send a couple of low pressure systems south of the Aleutians and into the Gulf of Alaska, Wed-Fri, and again by Sat-Sun. With the first one, which could become a fairly deep cyclone (several solutions suggesting a central pressure as low 980mb), the deterministic guidance has shown better agreement compared to previous days on this, but some uncertainty remains on exact placement of the low, the details of which should get ironed out as we get closer in time. The 12z ECMWF was displaced north of the best consensus and closer to the southern AK coast, which would obviously have stronger weather hazard impacts for the southern coast into the Panhandle region. At this time, WPC preferred a more southerly solution, closer to the 12z GFS and CMC, which also fit well with the ensemble means and previous WPC continuity. The next shortwave moves into the region next weekend but the deterministic guidance shows bigger timing and strength issues. There is good agreement in placement with the ensemble means, but obviously in a much weaker state. The WPC forecast for days 7 and 8 leaned more heavily on the ensemble means, while still maintaining some modest percentages of the ECMWF and GFS just for a little bit of added system definition. ...Sensible Weather... A wet pattern will remain through next week across the Panhandle region as one system exits into western Canada on Wednesday and the next one moves into the Gulf. Moderate to locally heavy rainfall is likely from this main low Thursday and Friday not only across the Panhandle, but also along parts of the southern and southeast mainland coast. A track closer to the coast could mean greater impacts so there's plenty of uncertainty regarding exact locations and timing of heaviest precipitation. Regardless though, many models suggest a modestly deep surface low which likely will bring marine hazards and gusty winds to coastal locations as well later next week. A cold front pushing through western Alaska will likely bring some enhanced precipitation as well, especially for terrain areas, with some precipitation in the form of snow. With general southerly moist flow, cloudy conditions are likely through the period over much of the state. High temperatures should trend cooler through the week as the upper low becomes established over the Bering Sea, but morning lows should remain above normal across almost all of Alaska, with the warmest anomalies across the northern half of the mainland. 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 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