Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 738 PM EDT Sat Aug 12 2023 Valid 12Z Wed Aug 16 2023 - 12Z Sun Aug 20 2023 ...General Overview... The forecast period will begin on Wednesday with a broad upper low centered over the Kenai Peninsula that will continue to weaken, with a surface low moving onshore. The polar vortex may approach the Arctic coast later in the week, but the coldest weather and the core of the low should stay north of the state. The upper ridge that has persisted over the mainland is forecast to weaken further through the week and lead to more seasonal temperatures across the region by next weekend. ...Guidance Evaluation/Preferences... The 12Z model guidance suite is in generally good agreement for the middle of next week, but that changes going into Thursday night and beyond with multiple timing and amplitude differences across the north Pacific and Gulf region. The CMC is more in line with the model consensus compared to earlier runs that were more out of phase across the north Pacific. The GFS is stronger with a low approaching the central Aleutians compared to the other guidance by late Friday and into Saturday. Taking these factors into account, the fronts/pressures forecast is primarily derived from a nearly multi-deterministic model blend through Thursday, and then slightly reducing the use of the GFS and CMC by end of the forecast period, whilst increasing use of the ensemble means to about 50% by next weekend. ...Weather/Hazards Highlights... The heaviest precipitation is expected to be on Wednesday across the southern coastal areas and adjacent mountain ranges, and this will include northern portions of the southeast Panhandle, where 1 to locally 3 inches of rainfall will be possible as moisture surges inland ahead of a weakening surface low over the Gulf. Things will improve across this region going into the end of the week and beyond. A chilly rain is also appearing more likely across portions of the northwestern mainland by the end of the week as moisture intercepts the slow moving polar front. Temperatures are expected to generally be slightly above average across of the Interior region through the end of the week, and slightly cooler than average across southern portions of the state where clouds and rain will be more prevalent through Friday. Depending on how far south the polar vortex gets, below average temperatures are also expected to settle in across portions of the northwestern mainland by Friday and into next weekend. 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