Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 638 PM EDT Wed May 27 2020 Valid 12Z Sun May 31 2020 - 12Z Thu Jun 04 2020 ...Overview and Weather Hazards/Threats... A mid/upper-level ridge centered across the arctic just north of Alaska is expected to slowly weaken through the extended forecast period. The ridge will promote well above average temperatures for much of mainland Alaska (especially western mainland and the Interior) through early next week - with forecast highs ranging from 5 to as much as 20 deg F above average. Temperatures may approach 80 deg at a few locations across the Interior. Meanwhile, an active and somewhat blocked pattern farther south will keep persistent negative height anomalies in place across the North Pacific from near/south of the Aleutians, gradually migrating east into the Gulf of Alaska. As the upper low moves into the Gulf of Alaska, with a weakened upper ridge persisting in the Arctic, easterly flow is expected to develop across much of the Interior. This easterly flow will spread deeper moisture into the Interior as well, with precipitation chances increasing early next week. A weakening barotropic low in the Gulf of Alaska on Sun is expected to dissipate as another low pressure system passes near/south of the Aleutians Sun-Mon and enters the Gulf of Alaska on Tue. The leading system in the Gulf of Alaska will keep onshore flow in place, with rain and mountain snow expected across southern mainland and Southeast Alaska. Areas of showers will also cross the Aleutians in association with the next system. As the system reaches the Gulf by early next week, precipitation across southern mainland Alaska should become more widespread, with moisture (and scattered precipitation). ...Guidance/Predictability Assessment... A blend of the 12Z ECMWF/GFS was used as a basis for the forecast during days 4-6 (Sun-Tue). Overall model consensus during the first half of the extended period was improved relative to 24 hours ago. Despite appearing as an outlier yesterday with a faster eastward progression of the low pressure system into the Gulf of Alaska, the overall guidance consensus has now shifted in toward that idea. Starting on day 7 (Wed) and continuing through day 8 (Thu), weighting of ensemble means (ECENS and GEFS) was gradually boosted to comprise a majority of the forecast weighting. Ryan 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: - Much above normal temperatures for portions of mainland Alaska, Sat-Tue, May 30-Jun 2. 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