Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 754 PM EDT Fri Oct 20 2023 Valid 12Z Tue Oct 24 2023 - 12Z Sat Oct 28 2023 ...Synoptic Overview... The upper trough that will initially be in place across much of Alaska this weekend is expected to lift out and get replaced by a building upper ridge from the Gulf of Alaska to start next week. The anomalous ridge will likely serve as an atmospheric road block to storm systems over eastern Siberia and the western Bering, and keep much of the state dry. Some warm advection precipitation is expected for the northwestern quadrant of the mainland early in the week, along with strong winds near the western coast as a storm low pressure system lifts northward towards the Arctic across eastern Siberia. Most of the mainland should remain dry. ...Guidance Evaluation and Preferences... The 12Z model guidance suite has a good overall depiction of the synoptic scale pattern across the Alaska domain to start early next week, and therefore a general deterministic model blend suffices as a good starting point in the forecast process on Tuesday. The models still agree strongly on a warm frontal passage across much of the mainland for early next week. There is also good model agreement on the upper ridge axis building north from the eastern Gulf to the mainland by the middle of the week. Similar to yesterday, the greatest model differences by mid to late week are across eastern Siberia and also across the Arctic Ocean. There has also been a trend in the guidance to slowly bring the North Pacific storm system towards the north by late week. The ensemble means accounted for about half of the forecast for fronts/pressures by the end of next week and into next Saturday. ...Weather and Hazards Highlights... A moderating trend is expected to commence in terms of temperatures across much of the state by Monday as the departing trough gets replaced by a warm front and a building upper ridge across the mainland. There may still be some lows close to zero across the normally colder spots in the Interior, but most inland areas should have lows in the 10s and 20s going into mid-week, and highs 25 to 35 degrees, and low to mid 40s near the southern coastal areas. Temperatures will also be highly dependent on whether valley inversions can mix out during the day, but if they don't, temperatures may actually be colder than average for the lowest elevations of the Interior, while the surrounding hills may be considerably warmer owing to the ridge in place. An area of low pressure will cross through portions of the Bering Sea, clipping eastern Siberia before reaching into the Chukchi Sea through Monday night. It will spread light to locally moderate precipitation across much of the western to northwest Mainland, tapering off going into Tuesday as the warm air advection weakens. Gale force winds are also a good possibility for the northwestern coast early in the week, and this may lead to some coastal flooding issues. 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