Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 704 PM EDT Thu May 21 2020 Valid 12Z Mon May 25 2020 - 12Z Fri May 29 2020 ...Overview and Weather Hazards/Threats... A blocky large scale flow pattern over Alaska is expected to remain relatively unchanged next week. 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 of +15 deg F across the Interior into the Brooks Range. This will enhance snow/ice melt, so please refer to your local office for all seasonal river ice flow issues. A closed upper low and deepened surface system will gradually weaken while lifting northward on the western periphery of the upper ridge from the Aleutians/southern Bering Sea Sunday to the Arctic Ocean by next Thursday. A second closed upper low and deepened surface system will meanwhile organize over the northern Pacific early next week and is slated to slowly lift northward over the western Gulf of Alaska mid-later next week into/around the blocking upper ridge. Each of these systems offers a lingering wind/rain threat and an open water maritime hazard. ...Guidance/Predictability Assessment... Overall larger scale predictability across Alaska was above average due to a relatively stable and blocky flow regime. However, forecast spread is still quite evident with ridge evolution specifics and with significant developmental details of especially the second main low/system. Ensembles and WPC continuity lifted the low more rapidly over the west Gulf of Alaska through next midweek compared to the deterministic higher resolution 12 UTC model suite. The 12 UTC GFS seemed to best cluster with the GEFS/ECMWF ensemble means into early-mid next week before diverging more significantly. Accordingly, the WPC Alaskan medium range product suite was primarily derived from a composite blend of the 12 UTC GFS and GEFS/ECMWF ensemble means along with the 19 UTC National Blend of Models for days 4-8. The slower northward lift trend for the second main low in this scenario seems reasonable considering the nature of the blocking upper ridge. 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 precipitation across portions of southern Alaska, Sun, May 24. 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