Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 330 PM EST Tue Jan 15 2019 Valid 12Z Sat Jan 19 2019 - 12Z Wed Jan 23 2019 A multi-model signal shows the blocking pattern over Mainland Alaska transitioning a broad mean trough settling over the western/central Pacific and a building ridge over the eastern Pacific extending into northwestern North America. There is a general consensius pointing to one or more periods of enhanced precipitation/winds from the Aleutians across the Alaska Peninsula and southern coast to the Panhandle. The best performing guidance over the past couple of forecast packages was a compromise of the ECWMF and CMC. In collaboration with the Alaskan forecast offices, choose to utilize the ECMWF and CMC for this forecast package. These two models continue to depict the ridge over northern Alaska pushing northward as a low tracks from northwest Canada westward into northern Alaska. The GFS maintains this feature further East and does not reflect the recent pattern trend. A strong system is expected to track northward into the Gulf of Alaska during the weekend. The full model/ensemble envelope has a lot of east-west spread so there is still a risk of meaningful adjustment in future forecasts. Upper troughing that overspreads the western/central Pacific will favor evolution of multiple low pressure centers most likely to track along or just south of the Aleutians. The best agreement continues for one wave near the western Aleutians as of early Fri and then development of a stronger low south of the central Aleutians during the weekend. Thereafter models and ensembles show a variety of ideas involving leading triple point wave(s) to the east/northeast as well as for additional western Pacific features that may interact with or displace leading low pressure. Campbell/Rausch WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can be found at: http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html