Alaska Extended Forecast Discussion National Weather Service College Park MD 740 PM EDT Thu May 15 2025 Valid 12Z Mon 19 May 2025 - 12Z Fri 23 May 2025 ...Overview... Much of mainland Alaska remains situated between a cyclonic gyre over the Arctic and another gyre forecast to gradually migrate from south of the Aleutians toward the Gulf of Alaska through the medium-range period. Increasingly unsettled weather is expected to move into the Aleutians beginning midweek next week, while the Panhandle possibly receives moderately heavy precipitation amounts early next week. Some diurally-forced showers are expected to linger across the southern interior section of mainland Alaska. ...Guidance Evaluation and Preferences... Model guidance shows decent agreement on the above-mentioned pattern across the Alaskan domain through the medium-range period. Day 4/Monday should see a moderately strong cyclone heading fairly quickly eastward and passing south of the Alaska Panhandle. Models today have generally take this cyclone on a slightly farther south and faster easterly track compared with yesterday. The slightly more southern track has taken the heaviest rainfall farther south toward the southern end of the Panhandle on Monday. The system is forecast to decay significantly on Tuesday as it makes landfall in western Canada, resulting in precipitation gradually tapering off across the Panhandle. Behind this system, a weak wave should dip south of the Aleutians Monday and Tuesday, as the next moderately strong cyclone is forecast to approach western Aleutians. Since yesterday, the ECMWF has trended toward forecasting a much better-defined cyclone in much better agreement with the GFS/GEFS/CMC solutions. Ensemble means are showing decent agreement with carrying this cyclone on an east-southeastward track, passing to the south of the Gulf of Alaska into late next week when a ridge appears to build behind that cyclone. Ensemble means indicate that that the upper-level pattern from the Bering Sea southward will become increasingly amplified by later next week, with precipitation associated with the next cyclone reaching into the western Aleutians and Bering Sea. Meanwhile across the Arctic region, ensemble means continue to indicate a cyclonic gyre in the vicinity will dig a trough toward northern Alaska early next week before showing signs of lifting back north as we head into late next week. The WPC forecast was based on 40% from the 12Z ECMWF/00Z EC mean, 40% from the 06Z and 12Z GFS/GEFS, and 20% from the 12Z CMC/CMC mean, with increasing proportion from the ensemble means toward the end of the forecast period. WPC continuity is well maintained. ...Weather/Hazards Highlights... As the medium-range forecast period begins on Monday, the next cyclone should quickly bring increasing rain chances into the Panhandle, especially near the southern portion. This should be followed by a gradual tapering off of the rain on Tuesday. Increasingly unsettled weather is forecast to move into the western to central Aleutians from middle to late next week as rain associated with a couple of cyclones moves into the region under an increasingly amplified upper-level pattern over the Bering Sea and southward into the North Pacific. Meanwhile, temperatures across the central to southern section of mainland Alaska as well as the coastal plain of the North Slope should average above normal through midweek next week while the Southeast, Brooks Range, and the Aleutians should average below normal due to clouds and precipitation. Some terrain and diurnally-forced precipitation/convection can be expected across the southern interior section near a stationary boundary while some upslope snow is forecast for the central portion of the Brooks Range through the forecast period. A slow warming trend should bring temperatures averaging to slightly above normal level for the overall Alaskan domain by late next week. Kong 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