Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 736 PM EDT Mon Apr 15 2024 Valid 12Z Fri Apr 19 2024 - 12Z Tue Apr 23 2024 ...Synoptic Overview... An amplified upper level flow pattern is forecast to be in place across the Alaska domain for the end of the week, with a strong ridge axis and closed upper high situated over the Yukon Territory, and a broad upper low several hundred miles south of the Alaska Peninsula and weaker low over the northern Bering Sea. Onshore flow directed towards the coast will produce periods of moderate precipitation from the Alaska Peninsula to the Prince William Sound, and abating in intensity going into the weekend. A second area of low pressure will likely develop over the Aleutians by early next week with the Gulf low weakening over time, and a frontal boundary will be draped across the northern half of Alaska. ...Guidance Evaluation and Preferences... The 12Z model guidance suite, along with the 18Z GFS/GEFS mean, are in reasonably good synoptic scale agreement on Friday. The CMC takes the main Gulf low farther to the north by Saturday towards the coast, and this continues going into Sunday with its solution over the southern Bering with the surface low, while the consensus favors a position a few hundred miles south of Kodiak Island. Going into Monday, the GFS remains stronger with the Gulf low while the CMC/ECMWF weaken it substantially more. Model spread becomes noteworthy for the next low pressure system approaching the Aleutians/Bering Sea region for early next week, with the CMC well to the south of the GFS/ECMWF, and then the GFS is farther west with the main low going into next Tuesday. The WPC fronts/pressures forecast was primarily derived from a multi-deterministic model blend on Friday, and then gradually increasing percentages of the ensemble means through next Tuesday as storm system differences become larger. Lesser weighting was applied to the CMC solution given the differences noted. ...Weather/Hazards Highlights... Coastal rain and mountain snow is expected to be moderate to locally heavy going into the second half of the work week from the southern Alaska Peninsula to the Prince William Sound region with continuing onshore flow northeast of the Gulf low, with the heaviest precipitation likely on Thursday. There should be gradual abatement in the precipitation going into the weekend as the moisture flux towards the coast weakens. Lighter showers are possible farther inland across western portions of mainland Alaska. Temperatures are generally expected to be pleasantly mild with readings in the upper 40s to upper 50s for highs across most Interior locations south of the Brooks Range, and generally 40-45 degrees near the southern coastal areas. A cooling trend is likely by early next week as the upper ridge axis breaks down. The Brooks Range will be the demarcation for much colder conditions across the North Slope and extending to the Arctic Coast. 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