Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 631 PM EDT Thu May 28 2020 Valid 12Z Mon Jun 01 2020 - 12Z Fri Jun 05 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 western 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 rise into the 70s for some locations. 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. A relatively deep low pressure system is forecast to pass near/south of the Aleutians though Mon/early Tue before entering the Gulf of Alaska. Persistent onshore flow is expected ahead of the system, with rain and mountain snow expected across southern mainland and Southeast Alaska. Areas of showers will also cross the Aleutians in association with the incoming system. As the low pressure system reaches the Gulf, precipitation across southern mainland Alaska should become more widespread, with moisture (and scattered precipitation). ...Guidance/Predictability Assessment... Deterministic models have continued to struggle with the timing of the Aleutian/Gulf low pressure system, with the ECMWF/GFS both showing a relatively large degree of variability and inconsistency today after seemingly better consensus yesterday. Ensemble means continue to show a bit more consistency, and the 12Z UKMET was the deterministic solution (through early day 6) that fit best with the ensemble means and within the center of the overall ensemble spread. Thus, a blend of the UKMET along with ECENS/GEFS ensemble means was used during days 4-6 (Mon-Wed), with the blend for days 7-8 (beyond the time range of the UKMET) comprised entirely of ensemble means. 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 western Alaska, Sun-Mon, May 31-Jun 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