Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 327 PM EDT Mon Apr 15 2019 Valid 12Z Fri Apr 19 2019 - 12Z Tue Apr 23 2019 Models/ensembles show broad consensus that upper ridging should persist/expand across eastern Russia and the western Bering Sea during the extended forecast period. A strong jet across the north Pacific will undercut the ridge with a stream of shortwave energy feeding into and reinforcing a mean upper-level trough extending from mainland Alaska south into the Gulf of Alaska. Shortwave energy spilling over the crest of the ridge will also move south across the eastern Bering Sea throughout the period, interacting with the mean trough as well as energy from the north Pacific, introducing an additional degree of complexity/chaos to the forecast and reducing predictability by the latter portion of the forecast period. Consensus has improved surrounding a low pressure system expected to move north across the Gulf of Alaska on Sat. The ECMWF and GFS solutions both lied within a fairly well-clustered consensus of ensemble members through Sat. After this time spread begins to increase gradually as arctic shortwave energy dives south and enters the mean trough, reinforcing a deep upper low across the Gulf. While models handle this evolution differently, they all show a similar result with a highly occluded low remaining in the Gulf as the front sweeps inland and weakens. The low should persist in the Gulf in some form into early next week, with even some degree of ensemble clustering evident around this feature through day 8 (Tue), although the specific position of the feature remains unclear, with members ranging from just of the Alaska Peninsula to the eastern Gulf just off the Alaska Panhandle. Given these considerations, the forecast was initially based heavily on a blend of the ECMWF/GFS during days 4-5 (Fri-Sat), with a gradual trend toward heavier weighting of ensemble means (ECENS and GEFS) from day 6 (Sun) onward. Ryan Bullet points from the WPC Days 3-7 Hazards chart can be found at: https://www.wpc.ncep.noaa.gov/threats/threats.php - Heavy rain across portions of the Alaska Panhandle, Thu-Fri, Apr 18-Apr 19. 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