Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 553 PM EDT Mon May 25 2020 Valid 12Z Fri May 29 2020 - 12Z Tue Jun 02 2020 ...Guidance/Predictability Assessment... Alaskan medium range forecast predictability remains generally above average due to a relatively stable and blocky larger scale flow regime, but quite a bit of uncertainty still builds over time with offshore lows and with small scale weather features embedded within the larger scale flow. Accordingly, the WPC Alaskan medium range product suite was primarily derived from a composite blend of well clustered guidance of the 12 UTC GFS/ECMWF, GEFS/ECMWF ensemble means and the 19 UTC National Blend of Models Friday into Sunday. Quickly transitioned blend weightings away from the deterministic models amid growing uncertainty next week, but applied manual adjustments to ensure offshore low strengths consistent with upper support. This maintains decent WPC continuity. ...Overview and Weather Hazards/Threats... An amplified upper-level ridge lingers from the Arctic Ocean to eastern Alaska and northwest Canada. This will support above average temperatures with anomalies upwards of 15 deg F over the Brooks Range and vicinity. This will enhance snow/ice melt, so please refer to your local office for any seasonal river ice flow issues. A deepened east Pacific low will lift northward into the eastern Gulf of Alaska mid-late week. Maritime wind/rain impacts may modestly affect Southeast Alaska. The system should slowly weaken and meander over the northern Gulf of Alaska next weekend, blocked underneath the upper ridge. Meanwhile, a surface system will continue to weaken and lift northward on the northwestern periphery of the upper ridge to the Arctic Ocean by Friday. Another low in the wake of this system is expected to meanwhile dissipate over the far southwest Bering Sea. A slow moving and deepened north Pacific low is then slated to bring wrapping winds/rains to the Aleutians this weekend then onward to the Alaska Peninsula and southern Alaska early next week. The low would also present an organized maritime hazard. Triple point low re-development and some system energy phasing may spread activity downstream across the Gulf of Alaska early next week. Schichtel 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 southern mainland Alaska and the Aleutians, Mon, Jun 1. - Much above normal temperatures for parts of northern mainland Alaska, Thu-Mon, May 28-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