Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 632 PM EDT Tue Apr 20 2021 Valid 12Z Sat Apr 24 2021 - 12Z Wed Apr 28 2021 ...Overview and Guidance/Uncertainty Assessment... An overall quiet weather pattern is on tap for much of Alaska days 4-8. Latest guidance continues to depict a fairly blocky regime during much of the extended range period, with a slowly westward retrograding upper ridge/closed high dominating much of mainland Alaska as ample northwest Canadian closed vortex energies slowly work into the state. The period begins Saturday with a lead 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 5, the pattern may consolidate into a main low just south of the Aleutians as energies slide more underneath the closed high. This will favor organized low pressure system development at the surface. Models still vary on the evolution and track of this low, related to uncertain ridge transformation details over the mainland. Prefer persistence more than transition in blocky patterns. Accordingly, the WPC forecast for today used a blend of best clustered guidance of the 12 UTC GFS/ECMWF and 12 UTC GEFS/ECMWF ensemble means with a focus on the models days 4/5 transitioning to the ensemble means into days 6-8 consistent with growing forecast spread. ...Weather/Hazards Highlights... Most of Alaska should remain warm and dry through much of the period, with precipitation confined to the Aleutians/Alaska Peninsula and vicinity, particularly associated with the low pressure system Saturday into Monday as it drifts over or just south of the islands. Light to moderate amounts are most likely. A period of gusty winds and unsettled maritime conditions are also likely in association 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, especially through the coming weekend. Lowering heights over northern and eastern Alaska early next week should help to moderate temperatures back towards normal or even below as the pattern aloft will tend to retrograde westward and allow frontal passage. Elsewhere, the southeast should experience near or below normal temperatures through the medium range period in offshore flow to the north of a slowly exiting southeast Gulf of Alaska low. Schichtel Hazards: -Much above normal temperatures across portions of mainland Alaska, Fri-Mon, Apr 23-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