Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 441 PM EDT Sat Apr 12 2025 Valid 12Z Wed 16 Apr 2025 - 12Z Sun 20 Apr 2025 ...Potent storm to offer heavy precipitation and high wind/wave threats for the southern tier of Alaska and the northern Gulf of Alaska Tuesday-Thursday... ...Guidance/Predictability Assessment... Favor a blend of the 12 UTC GFS/ECMWF/UKMET/Canadian models and best supporting GEFS/ECMWF ensemble means to address now less certain short to medium range time scale stream phasing aloft and associated surface system focus. However, the overall pattern evolution still seems to offer better than normal predictability through medium range time scales. Manual adjustments ensured sufficient offshore low strengths to compensate for the broad blending process given overall favorable support. WPC product continuity was well maintained with this plan. ...Weather/Hazards Highlights... There remains good support for the development and northward track of a deep low from the Northern Pacific towards the eastern Aleutians and Alaska Peninsula/Bristol Bay amd vicinity Tuesday into Thursday, with weakening system energies and precipitation propagating and reforming over the northern Gulf of Alaska and vicinity Friday into next weekend. The deepened main surface system evolution is a bit chaotic given early period uncertainties with upper flow phasing, but should eventually consolidate given amplified upper low/trough support aloft and coupled downstream upper ridging to act to slow eastward progression. Mean moist southerly flow wrapping near and east of the low will focus a multi-day period with locally heavy precipitation potential from southern Alaska into portions of Southeast Alaska, mainly Tuesday into Thursday. In this period of deepest low strength and pressure gradients, northerly winds and gap winds on the backside of the low both over the eastern Aleutians and the Alaska Peninsula as well as with leading winds up through Kodiak Island and southern Alaskan coastal areas through especially the Alaska Range may prove quite strong and gusty. The low will also present a well organized maritime hazard to monitor. While additional influx of upper through energies will meanwhile work up into/over the Interior, significant moisture or more than localized pockets of snow are not expected there. Meanwhile, there is also a growing signal supporting another deepened upper trough/low approach well upstream to the Aleutians later next week and weekend that offers a threat for organized rains and enhanced winds/waves to monitor in the coming days. Schichtel Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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