Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 250 PM EST Sat Mar 09 2019 Valid 12Z Wed Mar 13 2019 - 12Z Sun Mar 17 2019 Predictability across Alaska is slightly above average during the early portion of the extended period (Wed-Thu), and near to slightly below average by the latter portion of the period. Confidence is relatively good with respect to the large scale flow pattern across the region, with persistent mean upper-level troughing near the Aleutians, and an upper ridge axis rebuilding across western/northwestern Canada, into portions of mainland and Southeast Alaska by late in the period. This setup will keep the preferred storm track near/south of the Aleutians and into the Gulf of Alaska, with persistent southerly flow into Alaska. Models/ensemble members showed good clustering surrounding a relatively strong low pressure system entering the Gulf Wed and then moving onshore in the Alaska Peninsula or southern mainland Alaska by Thu. By later Thu this system should weaken as it moves inland and merges with a broader area of shortwave energy farther north. The forecast during days 3-4 was based heavily on a blend of the ECMWF/CMC solutions, which showed relatively good consensus during this time frame, and maintained good forecast continuity. In the wake of this Wed-Thu system, the flow becomes a bit more chaotic, with a couple smaller scale shortwaves expected to skirt south of the Aleutians and eventually move into the Gulf. Models suggest some consolidation of shortwave energy into a closed low south of the Aleutians by next Fri-Sat, likely associated with another deep surface low. Additional uncertainty arises in the handling of a couple areas of arctic shortwave energy exiting eastern Siberia during the middle to latter portion of next week, and whether they amplify across the Bering Sea or remain confined closer to eastern Russia as a consolidated upper low. Given the increased spread, the forecast was trended toward heavier ensemble mean (ECENS/NAEFS) on day 6 (Fri), with majority ensemble means during days 7-8 (Sat-Sun). Ryan Bullet points from the WPC Days 3-7 Hazards chart: 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 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