Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 628 PM EDT Fri Jul 23 2021 Valid 12Z Tue Jul 27 2021 - 12Z Sat Jul 31 2021 ...Guidance/Predictability Evaluation... A stagnant cutoff low in the Gulf of Alaska will weaken but meander in the region through much of the extended range period. This should allow for upper level ridging to build into the eastern part of the mainland. Meanwhile, a deep upper low will move into eastern Russia as heights lower across the Bering Sea and eventually the Aleutians. After day 5, the guidance continues to show significant uncertainty regarding the Bering Sea trough and smaller scale pieces of energy which may undercut the trough and move over or south of the Aleutians. Given the uncertainty, the WPC forecast trended quickly towards the ensemble means days 5-7, with some minor contribution from the 12z GFS which was the deterministic solution closest to the means. ...Weather/Threats Highlights... The main areas of precipitation and unsettled weather will be focused across the western and northwestern mainland throughout the period as southerly flow ahead of the Bering Sea trough interacts with a cold front and stalled stationary boundary across the northern Mainland. The best chance for heavier precipitation will be Tuesday and Wednesday across parts of the Seward Peninsula, and northward. Moderate to locally heavy rains may continue after Wednesday, but confidence in the amounts and particular locations remains low at this time. High waves and gusty winds may also present themselves for the west coast mainland. Troughing extending into the Bering Sea and Aleutians later in the week could lead to some higher waves and precipitation for parts of the Aleutians into next weekend. For western and northern parts of Alaska, temperatures should remain below normal, but should trend warmer for eastern parts of the state as upper level ridging builds in aloft. Santorelli Hazards: - Heavy rain across portions of mainland Alaska, Tue-Wed, Jul 27-Jul 28. Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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