Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 746 PM EDT Mon Aug 14 2023 Valid 12Z Fri Aug 18 2023 - 12Z Tue Aug 22 2023 ...General Overview... One of the main features of interest for the end of the work week will be a polar vortex that will loiter just north of the Arctic Coast with its cold front making it to the Brooks Range through the weekend. There will likely be another low that approaches the eastern Aleutians and Alaska Panhandle region on Saturday, and then attention turns to the west as the extratropical low from what is currently Typhoon Lan enters the Bering Sea region by late Sunday and into early next week with increasing rain and winds for western portions of the mainland and the Aleutians. ...Guidance Evaluation/Preferences... The 12Z model guidance suite featured good overall agreement among the UKMET/GFS/ECMWF and the ensemble means. The CMC was the exception to this with its upper low/trough much farther east across the northern Gulf with the storm system approaching this weekend, and thus out of phase with the model consensus for upper level ridging across the northeast Gulf. The UKMET was centered to the east of the model consensus with the position of the polar vortex, so the low position was adjusted to more closely match the ensemble means. There has also been a faster trend in the guidance over the past few model cycles regarding the track of the extratropical low associated with Typhoon Lan, and the updated forecast reflects this. The fronts/pressures forecast is primarily derived from a UKMET/GFS/ECMWF blend through Sunday, and then increasing use of the ensemble means to about 50% early next week whilst still keeping some of the operational GFS and ECMWF and none of the CMC. ...Weather/Hazards Highlights... Improving weather conditions can be expected for the southern coast and the southeast Panhandle region to close out the work week with showers becoming more isolated to scattered in coverage, and this pattern continues going into Saturday. Another round of showers is likely from the Alaska Peninsula to the Kenai Peninsula by Sunday with the approach of the next storm system, but overall amounts should be light to moderate in most cases. Elsewhere, rainfall is forecast to increase in coverage across north-central portions of the mainland as a slow moving cold front drops south from the Arctic, with the potential for scattered 1-2 inch rainfall totals over the Thursday through Sunday night time period. Depending on how far south the polar vortex gets, below average temperatures are expected to settle in across portions of the North Slope and Brooks Range by Friday and into next weekend. Near to slightly above temperatures are expected elsewhere across the state. 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