Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 646 PM EST Tue Jan 14 2020 Valid 12Z Sat Jan 18 2020 - 12Z Wed Jan 22 2020 ...Overview... Most guidance shows an evolution toward a period of upper troughing from Siberia into the northeastern Pacific/Gulf of Alaska as an upper ridge initially over the North Slope and northwest Canada rapidly rotates to the north and east. There will also be a fairly progressive North Pacific/Aleutians/Bering stream that will feed into the mean trough. This pattern will promote a moderating trend from the well below normal temperatures across the Panhandle and southern half of the mainland at the start of the period. Expect the primary precipitation focus to be over the Panhandle and westward to around the eastern part of the Kenai Peninsula with one or more northeastern Pacific/Gulf waves. The Aleutians should see some light precipitation through the weekend, followed by the possible arrival of an organized area of moisture associated with a North Pacific system by Tue-Wed. ...Guidance/Predictability Assessment... In spite of the agreement for the overall pattern evolution, there are multiple uncertainties with forecast specifics--especially for features across the North Pacific and into the Gulf of Alaska. Early in the period a blend of the 00Z/12Z ECMWF runs and 06Z/12Z GFS provides better definition than the ensemble means while still accounting for detail spread that already exists at this time frame. This consensus depicts energy initially near the Alaska Peninsula organizing into a compact upper low that tracks north-northwest along the western coast of the mainland and/or the western tip of Siberia, possibly interacting with separate upper low/trough energy that approaches from the west. As this occurs expect surface low pressure to evolve over the eastern/northern Bering, eventually lifting northward along with the upper dynamics. Meanwhile low pressure should track northward into the Gulf during the first half of the period, with the best cluster suggesting it may reach somewhat north of the 12Z GFS. Confidence decreases for specifics of one or more trailing waves over the northeastern Pacific/Gulf. There is a decent cluster of guidance signaling a fairly strong North Pacific system that could have some influence on the Aleutians by Tue-Wed. Over the past day GFS/ECMWF/ECMWF mean/CMC runs have been consistent in depicting this system albeit with considerable latitude and timing spread. Latest ECMWF runs have been in the northern part of the spread as was the 00Z CMC. The 12Z CMC adjusted somewhat south/east, while GFS runs and the ECMWF mean are more suppressed due to keeping southern Bering flow flatter (versus the upper ridge that develops in the operational ECMWF). An intermediate solution currently appears best given the CMC trend and ECMWF mean runs that are closer in principle to the GFS. ...Weather/Hazards Highlights... Southern portions of the mainland as well as the Panhandle will see a warming trend from below normal temperatures this weekend. Some pockets of above normal readings may be possible over the southeastern corner of the mainland by next week. The North Slope and vicinity should see above normal temperatures, with greatest anomalies on Sat. Expect the best focus for precipitation to extend between the eastern Kenai Peninsula and the Panhandle from Sun into next week with one or more waves reaching the Gulf. Activity could be locally moderate to heavy at times. The Aleutians will see light to isolated moderate precipitation through the weekend into early next week, followed by uncertain coverage/intensity of organized precipitation depending on the track of the system to the south. Rausch Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php - Much below normal temperatures across portions of the Alaska Panhandle and mainland Alaska, Fri-Sun, Jan 17-Jan 19. - Much below normal temperatures across portions of the Alaska Panhandle, Fri-Sat, Jan 17-Jan 18. 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