Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 702 PM EDT Mon Apr 19 2021 Valid 12Z Fri Apr 23 2021 - 12Z Tue Apr 27 2021 ...Overview and Guidance/Uncertainty Assessment... Latest guidance continues to depict a fairly blocky regime during much of the extended range period, with upper ridging dominating much of mainland Alaska. The period begins Friday with one system moving through the N. Pacific towards the Northwestern U.S. coast as a couple of closed lows/systems make their way towards the Aleutians. By Sunday/day 6, the pattern should consolidate into one main low just south of the central/eastern Aleutians with an organized low pressure system at the surface. After this, models begin to diverge on the evolution and track of this low, related to how quickly the ridge wants to break down over the mainland. Contrary to previous days, the 12z GFS is now the quickest to break down the ridge which pulls the Aleutians low north into the Bering Sea days 7-8. The 12z ECMWF/CMC both suggest the ridge holds strong and forces the low eastward towards the N. Pacific (also with support from the ensemble means). The WPC forecast for today used a composite blend of mostly 12z GFS/ECMWF/CMC through day 6. For days 7 and 8, removed the GFS from the blend in favor of more ensemble mean contribution as well as smaller percentages of the ECMWF/CMC for added detail and system definition. This approach fits well with yesterdays continuity as well as the preference downstream over the CONUS. ...Weather/Hazards Highlights... Most of Alaska should remain warm and dry through the period, with any precipitation confined to the Aleutians/Alaska Peninsula and vicinity, particularly associated with the low pressure system Sunday into Monday as it drifts over or just south of the islands. Light to moderate amounts are most likely, though some locally higher totals could be possible depending on exact strength and track of the low. A period of gusty winds are also likely in associated with this storm. The vast majority of the state should be well above normal in terms of temperatures through much of the period, with the warmest anomalies over the North Slope region and western areas of the Mainland (with even more anomalous warm morning lows). Lowering heights across eastern Alaska early next week should help to moderate temperatures a bit back towards normal or even below. The exception to all this warmth will be in the southeast quadrant and much of the Panhandle where temperatures should be near or below normal the entire medium range period. Santorelli Hazards: -Much above normal temperatures across portions of mainland Alaska, Thu-Mon, Apr 22-Apr 26. 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