Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 645 PM EDT Wed Apr 15 2020 Valid 12Z Sun Apr 19 2020 - 12Z Thu Apr 23 2020 ...Overview and Guidance Evaluation... It appears that considerable forecast uncertainty will persist through the medium-range period from the Aleutians southward next week. In fact, the model spread has not improved since yesterday. The ECMWF still likes to favor a stronger system farther downstream while the GFS keeps the stronger system near the Aleutians. The CMC is somewhere in between but closer to the GFS solutions. The ensemble means also show similar differences in the placement of the cyclone center, with the GEFS and the Canadian mean keep the center close to the central Aleutians while the EC mean puts it quite a bit to the east. By Day 8 Thursday, the EC mean deepens an upstream vortex and results in a pattern much more similar to the GEFS and the Canadian mean. In general, the guidance is slowly nudging the cyclone track farther south or offshore from the Aleutians, including the 12Z EC mean, which continues to maintain a stronger cyclone to the east. The WPC pressure fields were derived using a consensus of the 00Z EC mean and the 12Z NAEFS together with the 12Z ECMWF and the 06Z and 12Z GFS. More of the ensemble means were used for the longer range period but leaning slightly toward the 00Z EC mean. The results agree fairly well with WPC continuity. Models are much more agreeable for other areas of Alaska. The stationary ridge over Alaska should gradually get weaker with time while the arctic air farther north is forecast to edge closer toward Alaska and then slide off to the east. ...Weather/Threats Highlights... Expect a broad area of precipitation to cross Alaska to close the weekend, due to an initially strong low level flow ahead of a dissipating front moving into the western mainland and a weakening low pressure system over Aleutians/Bering Sea. The wavy front persisting across the northern mainland for most of the period will also provide a precipitation focus. It appears the the heaviest precipitation will initially be focused across the southern sections of the state. Beginning early next week, the large scale pattern evolution should promote a drier trend over much of the mainland. Despite the forecast uncertainties, parts of the Aleutians should see meaningful precipitation/gusty winds depending on the precise surface evolution through next week. The temperature forecast looks consistent, with above normal temperatures over most of the state during the period aside from the Panhandle and major valleys over the southern mainland where highs may be modestly below normal. Morning lows should tend to be farther above normal than daytime highs and the northern mainland will likely see the highest anomalies. Multi-day trends have been toward a later southward push of the northern mainland front but it should eventually drift south next week as broadening cyclonic flow aloft over the Arctic begins to have some influence over the northern part of the state. Kong/Rausch 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 the Alaska Panhandle and mainland Alaska, Mon-Wed, Apr 20-Apr 22. - Heavy precipitation across portions of mainland Alaska, Sat-Sun, Apr 18-Apr 19. - Much above normal temperatures across portions of mainland Alaska, Sat-Mon, Apr 18-Apr 20. 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