Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 635 PM EDT Fri Jun 25 2021 Valid 12Z Tue Jun 29 2021 - 12Z Sat Jul 03 2021 ...Unsettled weather expected from portions of the Aleutians to the Southern Coast... ...Overview and Guidance/Predictability Evaluation... The latest models and ensembles continue to advertise that an upper low will drift slowly eastward to the south of the Aleutians before possibly shifting northward into the Bering Sea, potentially blocked by upper level ridging building over the Mainland late next week. Perturbations rounding the base of the trough will send a couple of waves of low pressure/systems into the Aleutians through the week, enhancing potential for wet and windy weather. Troughing may also briefly move through northern parts of Alaska before the strong ridging drives it eastward. Models and ensembles generally agree on this overall pattern, although continue to exhibit plenty of uncertainty regarding the details. There are some timing and strength differences with how quickly ridging builds into central and eastern Alaska, which would affect steering flow for the Aleutians low. By day 7-8, weaker ridging in the 12z ECMWF would want to pull the low farther east into the AK Peninsula, although the GFS (and the ensemble means) are more consistent with showing strong ridging which blocks eastward movement and pushes it north into the Bering Sea. As such, WPC trended towards a majority ensemble mean blend the latter half of the period, with some modest contributions from the 12z GFS for added system definition and details. The first half of the period leaned very heavily on the 12z operational ECMWF and GFS. This approach fits well with yesterdays continuity as well. ...Weather/Threats Highlights... Surface lows and fronts ejecting into the Aleutians towards mid next week is expected to set up a wet and windy pattern from especially the eastern Aleutians into the Alaska Peninsula and Kodiak Island/Lower Cook Inlet. This should bring moderate to locally heavy rainfall to the region, although exact amounts remain uncertain. Gusty winds and high waves may also accompany these systems as they cross the region. To the north, a cold front dropping through Northern Alaska may bring some modest precipitation to parts of the North Slope region and Brooks Range, with snow possible in the higher elevations. In terms of temperatures, upper troughing across the state early in the week will keep temperatures cool, especially across the Brooks Range and northern Slope region where daytime highs as much as 20 degrees below normal are possible. As upper level ridging builds over the state during the later half of next week, temperatures should warm to above normal, with pleasant highs in the 70s for parts of eastern Alaska. Southern Alaska and back to the Aleutians should remain near or below normal underneath cloudy skies and unsettled conditions. Santorelli 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 rain across portions of mainland Alaska and the Aleutians, Wed-Fri, Jun 30-Jul 2. - High winds across portions of mainland Alaska and the Aleutians, Wed-Thu, Jun 30-Jul 1. 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