Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 659 PM EST Wed Dec 07 2022 Valid 12Z Sun Dec 11 2022 - 12Z Thu Dec 15 2022 ...Overview... The latest runs of the deterministic models show a small improvement with a few features at different time periods, however the overall pattern has a large degree of forecast spread that remains to be resolved. The general consensus depicts a low pressure of moderate amplitude lift into the western Gulf and slowly tracks north and east. This feature will usher in a steady plume of deep moisture that will result in moderate precipitation that may be heavy at times from the Alaska Peninsula Sunday, across the Kenai Peninsula and surrounding area Monday and from the Valdez area and points east on Tuesday. Stronger gap winds may also arise as the low hangs out in the eastern Gulf. Generally light to moderate precipitation along with strong winds will spread over portions of the western/southwestern Alaska as shortwave energies pass from eastern Siberia across the Bering Sea. Although there continues to be variance with the ridge axis location, this feature has the most confidence through the extended forecast. With it progged to settle in over the eastern part of the state and into western Canada, colder air will reside over portion of the Southeast and eastern Mainland later in the period. ...Guidance/Predictability Assessment and Preferences... Initial smaller-medium scale systems involve a wave/frontal system over the Bering Sea/Aleutians, low pressure that may track along the northwest coast of the Bering Sea, and low pressure off the southeastern coast/Panhandle. Finally, low-predictability shortwave details will have a say in the details of low pressure initially over or near the Gulf of Alaska. The latest runs of the guidance continue to show a large degree of spread in amplitude, location and progression with several features but most notable is the system that should reach south of the Aleutians by early Saturday. For early next week the guidance has offered a general signal for one or more significant surface lows within an area from the northwestern Pacific into the Aleutians and western Bering Sea. The GFS depicted a notable slowing with the North Pacific low and the GEFS mean slowed a bit as well while the CMC trended a little more progressive similar to previous runs of the GFS. The WPC preferred blend began with a general consensus of the ECWMF/CMC/UKMET/GFS. Beyond Day 4 the UKMET was omitted. The ensemble means were introduced during Day 5 and steadily increased to about 50% by the end of the extended period. The previous forecasts utilized near 70% weighting of the means by Day 7/8 so this is a small improvement. ...Weather/Hazards Highlights... Well below normal temperatures will be in place over portions of southern/eastern Alaska as surface high pressure settles over portions of the mainland into western Canada early on. In contrast, a majority of the northwest half of the state is expected to maintain above normal temperatures, or moderate toward normal through the end of the forecast period. This gradient of surface pressure will likely lead to the presence of locally strong gap winds over the Gulf of Alaska/northeastern Pacific Ocean this weekend onward along the southern coast and Panhandle. The models continue to struggle coming to a consensus with the North Pacific low pressure that may affect the Aleutians and potentially parts of the western/southern mainland during the weekend into early next week, but there has been slight improvement. The latest trends continue to have areal averages of 1 to 2+ inches as it skirts eastward with isolated higher maximums. Once the precipitation moves inland or into areas of higher terrain it will likely transition over to all snow. Snow accumulations may end up be several inches daily with near/above 1 foot in the mountains. Finally, another system may affect some areas over the Aleutians and Bering Sea early next week with enhanced precipitation and wind but again the specifics are very uncertain at this time. Campbell Hazards: - Heavy precipitation across portions of mainland Alaska, Sun, Dec 11. - Heavy precipitation across portions of mainland Alaska and the Aleutians, Sat, Dec 10. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon, Dec 12. - High winds across portions of mainland Alaska, Sun, Dec 11. 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