Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 646 PM EDT Sat Apr 26 2025 Valid 12Z Wed 30 Apr 2025 - 12Z Sun 4 May 2025 ...Overview... For much of next week, a broad upper low is forecast to be in place near the Bering Sea, blocked in place by an Arctic ridge to the north and rounds of ridging over eastern Alaska and western Canada. Spokes of the trough may poke into western parts of the state at times. Meanwhile the storm track on the southern side of the upper low will lead to a cyclone approaching southeast Alaska and the Alaska Panhandle mid to late next week, bringing a heavy precipitation potential from the Alaska Peninsula eastward. Another Gulf low next weekend also bears watching, although it is currently forecast to remain farther south. ...Guidance/Predictability Assessment... The 12Z model guidance suite features good overall model agreement for the middle of the week, and therefore a deterministic model blend suffices as a good starting point in the forecast process. Looking ahead to the end of the week, timing differences become more apparent across the North Pacific, especially with the second system arriving by the weekend. The CMC becomes considerably slower with the arrival of that weekend system, and therefore more weighting was applied to the ECMWF/GFS and their ensemble means for the second half of the forecast period. ...Weather/Hazards Highlights... Late season heavy rainfall is still expected from eastern portions of the Alaska Peninsula to the southern mainland coast for the middle of the week. An atmospheric river is likely east of a northern Gulf low on Wednesday, with 2-4 inches of liquid equivalent for the south facing terrain. With the storm system and onshore flow weakening late in the week, an abatement of rainfall intensity and coverage is expected, with showers becoming more scattered in coverage. Depending on what the next system does next weekend, there may be a return of additional rainfall for the southern coastal areas, but as of right now, it appears the heaviest rainfall should remain offshore. A quasi-stationary frontal boundary draped across the Interior for most of the forecast period will separate a mild and spring-like airmass across south-central Alaska, from a much colder and polar-like airmass from the Brooks Range northward. Temperatures are generally expected to be below average with the Arctic surface high continuing to govern the overall weather pattern. Hamrick 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