Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 758 PM EDT Wed Oct 18 2023 Valid 12Z Sun Oct 22 2023 - 12Z Thu Oct 26 2023 ...Synoptic Overview... The synoptic pattern over Alaska this weekend through the middle of next week is expected to initially feature upper level troughing across much of the central and eastern Mainland, with generally cooler than normal temperatures and relatively lighter precipitation expected. By early next week, a stronger storm system will approach the Bering Sea and far eastern Russia, bringing widespread snow to parts of the northwestern Mainland due to warm air advection associated with the warm front. Temperatures are expected to warm up about 10-15 degrees or so compared to the weekend. ...Guidance Evaluation and Preferences... The 12Z model guidance suite has a good overall depiction of the synoptic scale pattern across the Alaska domain this weekend, and therefore a general deterministic model blend suffices as a good starting point in the forecast process. The models still agree strongly on a warm frontal passage across much of the mainland for early next week. There is also decent model agreement on the upper ridge axis building north from the eastern Gulf to the mainland by late in the forecast period, with the greatest model differences by this time residing across eastern Siberia and also across the Arctic Ocean where the ECWMF is stronger with the ridge axis. The ensemble means accounted for about 40-50% of the forecast for fronts/pressures by the middle of next week. ...Weather and Hazards Highlights... In the wake of the short term heavy rain event across the Southeast Alaska region, upper level troughing will prevail across much of the Mainland this weekend. This will bring generally cooler than normal temperatures and relatively lighter precipitation (or dry conditions), with widespread highs below freezing and overnight lows dropping into the 0s and 10s for many interior areas. Attention then turns to the storm system expected to brush western parts of the state early to middle next week. An area of low pressure will cross through portions of the Bering Sea, clipping eastern Russia before reaching into the Chukchi Sea. It will spread precipitation across much of the western to northwest Mainland, including the potential for widespread measurable snowfall where there is upslope enhancement across the western Brooks Range. Details on amounts and potential weather hazards are still uncertain this far out given some of the forecast model uncertainty, but it appears the overall magnitude of the expected precipitation has trended down some compared to yesterday's forecast. Gale force winds are also a good possibility for the northwestern coast early in the week. 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