Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 820 PM EDT Sun Sep 17 2023 Valid 12Z Fri Sep 22 2023 - 12Z Tue Sep 26 2023 ...Guidance Evaluation/Preferences... The 12Z model guidance suite is initially in good agreement late in the week, but model spread increases substantially going into the weekend and beyond with the timing and magnitude of storm systems crossing the Bering and the Gulf of Alaska. The CMC is likely too far north with the low entering the Bering Sea by Saturday, so a solution between the ECMWF/GFS was favored. The GFS is stronger than the model consensus with the development of the Gulf of Alaska trough by the weekend, so a slightly less amplified solution seems to work best for that area. The UKMET was out of phase across portions of the North Pacific beyond Thursday, so this solution was also not favored. The use of the ensemble means increased to about 50-60% by Sunday and Monday owing to increased uncertainty. ...Pattern Overview and Weather/Hazards Highlights... A rather unsettled weather pattern is expected across southeastern Alaska on Thursday with a deep surge of moisture from an atmospheric river event directed towards the Panhandle region, with perhaps 1-2 inches of widespread rainfall near the coastal mountains, and isolated 3 inch rainfall totals possible through Thursday night. The rainfall should abate some in coverage and intensity going into Friday as the Gulf low weakens. Attention then turns to the strong low pressure system entering the Bering Sea region by Friday and then reaching the western mainland by late Saturday. This will likely produce gale force winds over the coastal waters and an increase of rain and higher elevation snow for portions of western Alaska for the upcoming weekend. A third low pressure system may develop over the Gulf by Sunday/Monday and bring increased chances for additional rain and wind for the Panhandle region. In terms of temperatures, temperatures should generally be near to slightly above average for much of the mainland, equating to highs from the middle 40s to middle 50s for most locations, and slightly colder for locations north of the Brooks Range. 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