Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 531 PM EST Sat Dec 14 2019 Valid 12Z Wed Dec 18 2019 - 12Z Sun Dec 22 2019 A blend of the ECMWF/UKMET/CMC was preferred as a forecast starting point during days 4-5 (Wed-Thu). These solutions were relatively agreeable with respect to low pressure moving east across the Gulf of Alaska, while the GFS was on the western/southern fringe of the spread. Farther west, model consensus has improved with respect to a relatively deep low entering the western Bering Sea on day 5, and the aforementioned blend should resolve this system favorably. Farther north, upper ridging across the arctic is forecast to migrate toward Siberia during the early extended period, allowing arctic shortwave energy to carve out lower heights across the North Slope and the Interior, with most solutions showing an upper low developing across the North Slope by Fri. Also by days 6-8 (Fri-Sun), deterministic solutions show another wave of low pressure developing along an active North Pacific frontal zone, perhaps nearing the Aleutians by Sun. While models agree on the potential for this system, solutions vary widely on the track, timing, and intensity (although a number of solutions suggest the potential for a deep system). Given increased spread during days 6-8, went more heavily toward ECENS/NAEFS ensemble means during that time frame. This pattern should initially favor wet conditions across southern mainland Alaska very early in the extended period, the axis of best moisture should shift east into the Panhandle/Southeast Alaska from the middle of next week onward. Farther north, initially above average temperatures across much of the Interior will be replaced by below average temperatures as upper heights fall by early next week. Dry conditions should prevail across most of the Interior, however. Ryan Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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