Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 642 PM EDT Sat May 02 2020 Valid 12Z Wed May 06 2020 - 12Z Sun May 10 2020 ...Guidance/Predictability Assessment... Models/ensembles show relatively good consensus at the large scales through the extended forecast period, with a persistent trough/upper-level low south of Alaska across the North Pacific, and an upper-level ridge axis building from western Canada into mainland Alaska next week. This setup will eventually result in a pattern resembling a Rex Block, that will persist through and beyond the end of the extended forecast period. Even at smaller scales, deterministic model consensus is above average during days 4-5 (Wed-Thu) as one low pressure system fills south of the Gulf of Alaska and another weakens across the western Bering Sea. The above average consensus during this time frame lent to use of a 12Z ECMWF/GFS blend during days 4-5. By days 6-8 (Fri-Sun), the preferred storm track does not change substantially, but guidance spread gradually increases through time with the next low pressure system potentially approaching the western Aleutians late Fri into Sat, with some solutions taking the low into the southern Bering Sea and others keeping it farther south. Given the decent large scale agreement, opted to gradually increase weighting of ECENS/GEFS ensemble means through time, with majority weight on the means by days 7-8. ...Weather/Hazard Highlights... Persistent low pressure south of the Gulf of Alaska will keep onshore flow and precipitation, along with gusty winds, in the picture for the Alaska Peninsula and portions of southern mainland Alaska through the forecast period, especially by Thu-Fri as a weakening frontal boundary approaches. The western/central Aleutians will be subject to a couple rounds of rain and gusty winds Wed-Thu and again Sat-Sun as frontal systems affect the region. Rising heights across mainland Alaska as the upper ridge builds next week will promote warming temperatures. High temperatures are forecast to be 5 to 15 deg F above average across much of mainland Alaska from the middle of next week into next weekend, with temperatures potentially rising into the 60s for portions of the Interior. Ryan 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 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