Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 615 PM EDT Mon May 10 2021 Valid 12Z Fri May 14 2021 - 12Z Tue May 18 2021 ...Guidance/Predictability Assessment... 12 UTC GFS/ECMWF/Canadian model solutions seem fairly well clustered days 4-7 (Friday-next Monday). A composite blend in tandem with 19 UTC National Blend of Models guidance seems to produce a good forecast starting point consistent with a pattern with above normal predictability while maintaining good WPC product continuity. Jumped to use the latest ECMWF ensemble mean by day 8 that offers the best ensemble mean based system continuity from the day 4-7 model composite despite quickly growing forecast spread and uncertainty. ...Weather/Threats Highlights... Ejecting upper trough energies and precipitation focusing surface lows and associated frontal weather systems will work across the Gulf of Alaska to southeast Alaska into Friday, undercutting a warming and stabilizing interior upper ridge. Meanwhile upstream, amplified/closed upper trough energy is slated to track over the southern Bering Sea/Aleutians and deepening low pressure will support increasingly unsettled maritime conditions and inland feeding enhanced rains and winds across the region with frontal approach and passage. Activity is expected to translate downstream into Southwest Alaska, the Alaskan Peninsula, Kodiak Island, the Gulf of Alaska, the southern interior and then southern and southeast Alaska through next weekend into early next week with steady main system progression and lead triple point low developments and inflow. A second main low with enhanced rains/winds may meanwhile reach the Aleutians early next week. Guidance signal for this low is slowly growing, albeit with a less progressive latest trend. Schichtel Hazards: No significant hazards are expected over Alaska during this forecast period. 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