Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 748 PM EDT Wed Mar 11 2020 Valid 12Z Sun Mar 15 2020 - 12Z Thu Mar 19 2020 ...Overview and Guidance/Predictability Assessment... The forecast period begins on Sunday with an impressive upper level ridge and surface high anchored over the northern Gulf of Alaska, with 500mb heights approaching 576 dm. A storm system just south of the central Aleutians is forecast to weaken and then evolve into an open wave by Tuesday as it slowly lifts northward towards the western Alaska mainland. This will also serve to weaken the pronounced ridge over the Gulf some and shunt the ridge axis southward. Around the same time, a disturbance is progged to track eastward just north of the Arctic Coast, with the CMC and ECMWF tracking closest to the coast. There will be two noteworthy storm systems that will likely affect the Bering Sea region and the western Aleutians, with the first storm expected to affect mainly eastern Siberia and then weaken as it passes well to the northwest of the Alaska mainland. The second and potentially more impactful storm may impinge on the western Aleutians by early Wednesday and then reach the Bering by Wednesday night and into Thursday. Given that the GFS and ECMWF are indicating surface pressures near 970 mb and the CMC even stronger, along with good ensemble support, it is reasonable to expect that this will be the next major storm system to eventually affect the Alaska domain. The deterministic guidance has improved with the position of the storm, and the ECMWF is a little south of the model consensus. ...Weather Highlights/Threats... Western Alaska appears to be most favored for above normal precipitation for this time period as moisture advects northward around the western side of the large high pressure ridge, with several inches of snow likely for northwest portions of the state this weekend. Much of the eastern half of the state, and extending to the Panhandle region, should be mainly dry during this time. The other story will be the well above normal temperatures across inland sections of the state owing to the strong upper level ridge in place. Hamrick 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 Hazards: - Heavy snow across portions of northwest mainland Alaska, Wed, Mar 18. - Much above normal temperatures across portions of northern mainland Alaska, Sat-Wed, Mar 14-Mar 18. - Much below normal temperatures across portions of southeast mainland Alaska, Sat, Mar 14. 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