Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 618 PM EDT Sat May 23 2020 Valid 12Z Wed May 27 2020 - 12Z Sun May 31 2020 ...Guidance/Predictability Assessment... Forecast predictability over Alaska remains above average due to a relatively stable and blocky flow regime, but there has been more uncertainty with offshore lows. A composite of well clustered guidance from the 12 UTC GFS/ECMWF and GEFS/ECMWF ensemble means now seems reasonable Wednesday into Thursday. However, forecast spread quickly increases from that point forward offshore. The WPC Alaskan medium range product suite was mainly derived from a blend of best clustered guidance of the 12 UTC ECMWF and GEFS/ECMWF ensemble means along with the 19 UTC National Blend of Models. ...Overview and Weather Hazards/Threats... An amplified upper-level ridge is forecast to persist from the Arctic Ocean across eastern Alaska and into northwest Canada. This will result in above average temperatures with anomalies upwards to +20 deg F over northern Alaska. This will enhance snow/ice melt, so please refer to your local office for any seasonal river ice flow issues. A system well south of the state over the eastern Pacific mid-latitudes should organize early next week. This system has been difficult to track in guidance. However, latest models and ensembles now agree to lift a deepened low northward into the eastern Gulf of Alaska Wednesday/Thursday. Maritime wind/rain impacts may also affect Southeast Alaska. The system should weaken and meander over the northern Gulf of Alaska Friday into next weekend, blocked underneath the upper ridge. Meanwhile, an upper low and surface system will continue to weaken while lifting northward on the western periphery of the upper ridge from the Bering Sea midweek to the Arctic Ocean by Thursday. This system offers some lingering winds and precipitation. Another low in the wake of this system Wednesday-Friday is expected to hold over the southwest Bering Sea where it should dissipate. There is also an increasing guidance signal in support of subsequent development of a deeper Pacific low that is slated to work along with wrapping winds/rains toward the Aleutians into next weekend that would also present an organized maritime hazard. 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 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