Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 633 PM EDT Fri Mar 27 2020 Valid 12Z Tue Mar 31 2020 - 12Z Sat Apr 04 2020 ...Below to much below normal temperatures across portions of Alaska through the middle of next week... An anomalous upper-level high centered across northeast mainland Alaska early next week will displace arctic air southward to its east and southeast, keeping much of mainland Alaska cold through much of the week. High temperatures Tue-Thu are forecast to be 10-25 deg F below average across the southern half of mainland Alaska, as well as much of Southeast Alaska, with the arctic air mass expected to reinforce a persistent stationary frontal boundary just offshore. The North Slope will be the significant exception, where above normal temperatures are forecast through the medium range. Ensemble show a general consensus that the upper ridge should gradually weaken as it shifts eastward through the middle of next week, eventually breaking down the strong arctic connection and allowing temperatures across Alaska to begin slowly warming. Surface high pressure across mainland Alaska should keep conditions dry for many areas, while a relatively active storm track across the North Pacific remains mostly south of mainland Alaska, with some potential precipitation for the Aleutians, the Alaska Peninsula, and perhaps southwestern mainland Alaska (where heavy precipitation is possible by the middle of next week). Models/ensembles continue to show some degree of consensus on the idea of a deeper low pressure system moving into the Bering Sea next Thu-Fri, with a potential pattern change in the works for Alaska, as the removal of the blocking ridge present earlier in the week potentially opens Alaska up to somewhat more progressive westerly mid/upper-level flow (as shown by the GFS), or perhaps even a more amplified, but still relatively progressive flow regime (as indicated by the ECMWF). Ensemble means were generally somewhere in between these two scenarios, and were preferred by late next week. The WPC forecast was initially based heavily on the 12Z ECMWF/GFS, along with some use of the GEFS/ECENS ensemble means on day 4 (Tue). Starting on day 5 (Wed) and continuing through the remainder of the extended forecast period, a gradual trend toward heavier weight placed on ECENS/GEFS ensemble means was shown, to counter the increasing spread by that time (as described above). Ryan Hazards: - Heavy precipitation across portions of mainland Alaska and the Aleutians, Wed-Thu, Apr 1-2. - High winds across portions of the Alaska Panhandle and mainland Alaska, Mon, Mar 30. - Much below normal temperatures across portions of mainland Alaska, Mon-Tue, Mar 30-Mar 31. 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