Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 542 PM EST Thu Dec 12 2019 Valid 12Z Mon Dec 16 2019 - 12Z Fri Dec 20 2019 Models were relatively agreeable during the first portion of the extended forecast period, and a blend of the ECMWF/GFS/CMC was used as a forecast starting point during days 4-5 (Mon-Tue). These solutions showed relatively small timing and structural differences with a relatively deep low pressure system crossing the Aleutians during that time, and the described blend should resolve these differences favorably. From day 6 (Wed) onward, this system is forecast to move eastward, passing near or just south of the Alaska Peninsula and into the Gulf of Alaska. Timing differences among the guidance increase substantially from Wed onward, and a weighting of ECENS/GEFS ensemble means in the forecast was increased to account for this increased spread. Models/ensemble show some broad agreement that another relatively deep low pressure system should enter the western Bering Sea by day 7 (Thu), with guidance showing relatively large timing/structural differences that are best resolved at this point in time by going heavily toward the ensemble means. Some continued use (about 30%) of deterministic solutions was warranted through the end of the forecast period, however, to add a bit of definition to features beyond that shown by the ensemble means. In terms of sensible weather, this pattern should favor multiple round of precipitation across the Aleutians, Alaska Peninsula, southern mainland, and Southeast Alaska. Dry conditions should prevail across the mainland interior, however. Temperatures are forecast to be above average across southern mainland and across the North Slope through the extended period, with a trend toward slightly below normal temperatures across the interior by the middle of next week. Ryan Additional 3-7 Day Hazard information can be found on the WPC medium range hazards https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: No significant hazards are expected over Alaska during this forecast period. 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