Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Tue Aug 06 2024 Valid 12Z Sat Aug 10 2024 - 12Z Wed Aug 14 2024 ...A quick round of wind and moderate to locally heavy rain expected to move through the Aleutians into mainland Alaska this weekend... ...Overview... An amplified synoptic pattern will periodically spin energetic upper-level troughs across Bering Sea toward mainland Alaska through the medium-range period. These energetic troughs will then lift north to northeast across mainland Alaska ahead of an upper high that is forecast to remain anchored over northern Canada. One such disturbance will likely bring a quick round of wind and rain through the Aleutians into mainland Alaska this weekend before sliding across the southern coastline of Alaska early next week. The next system, which appears less robust than its predecessor, is forecast to move from Siberia into the Aleutians during the first half of next week. ...Guidance Evaluation/Preferences... For the upcoming system of interest, the ECMWF as well as the Canadian models are now going with a less-amplified and faster solution compared with the GFS solutions, which remain on the deeper and slower side as the cyclone traverses the Bering Sea from west to east on Friday and heading toward the west coast of Alaska on Saturday. Their ensemble means also show a similar discrepancy in the depth and speed for this system. The slower GFS and faster EC & CMC solutions carry downstream as well as the system pushes onshore into mainland Alaska. The next system of interest appears much less amplified as it ejects eastward from Kamchatka Peninsula into the Bering Sea by early next week. This system is characterized by a slower solution favored by the EC and CMC solutions in contrast with the faster motion by the GFS/GEFS, which is opposite of the model discrepancy exhibited in the first system. Thus the WPC forecast blend used a multi model deterministic and ensemble mean solutions from the 12Z GFS/GEFS, 12Z ECMWF/00Z EC mean, and 12Z CMC/CMC mean, leaning more toward the ensemble means by late in the period. This blend yielded a solution reasonably compatible with the previous WPC Alaska forecast package. ...Weather/Hazards Highlights... As the heavy rainfall event gradually comes to an end on Friday, the next energetic upper trough and relatively deep surface cyclone will head toward the west coast of Alaska on Saturday. This system appears to move at a relatively quick pace and bring a round of wind and rain through the Aleutians and into mainland Alaska this weekend. The rain is expected to be moderate to locally heavy through the Aleutians with winds possibly reaching 50 knots at times. Moderate to locally heavy rain is expected to overspread much of western Alaska through the weekend. The heaviest rainfall amounts are forecast to be farther downstream across portions of the terrain-favored locations of the southern coastline of Alaska as depicted on the Day 3-7 Hazards chart. The moisture will likely push through much of the rest of mainland Alaska through early next week with lighter amounts of rainfall and perhaps little to no rain across the North Slope. Meanwhile, the next system is forecast to bring widespread rainfall from west to east across the Aleutians during the first half of 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