Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 338 PM EDT Tue Apr 09 2019 Valid 12Z Sat Apr 13 2019 - 12Z Wed Apr 17 2019 The ensemble means are fairly similar and consistent with the general idea of low pressure tracking along the Aleutians during the weekend and then settling into a position southeast or east of Kodiak Island as mean troughing aloft becomes established near 150-160W longitude. Some ensemble mean runs have differed in precise details of individual features making up the overall trough. Not surprisingly individual model runs differ more greatly with North Pacific details, between faster progression of one or more features (as in 00-06Z GFS runs) or phasing that leads to at least temporary slower motion (12Z GFS). Based on guidance available through the 06Z cycle plus the 12Z GFS, the 00Z ECMWF and 06Z FV3 GFS compare most favorably to the ensemble means so preferences sided with those runs for emphasizing operational model detail especially early in the period. Arctic/Mainland details are of fairly small scale and not consistent over recent runs, so confidence in this part of the forecast is in the lower half of the spectrum. Currently there is a a decent consensus showing a ridge over the Arctic and a more modest cluster with a compact upper low over the northwest corner of the mainland (part of an overall weakness aloft over the mainland), with each feature lingering through the weekend into early next week. Model behavior so far suggests that further detail changes are likely in future runs. Late in the period the 00Z CMC and recent GFS runs runs show a stronger signal compared to the means for energy to round the upper ridge over the Bering and then amplify into the 150-160W mean trough. Lack of confidence in details at the late extended time frame would argue for a conservative forecast closer to the means for the time being. Based on above considerations today's forecast started with a blend of the 00Z ECMWF/ECMWF mean and 06Z FV3 GFS/GEFS mean. The early part of the forecast placed greater emphasis on the operational runs and the latter part focused more on the means, with subsequent editing as appropriate. Rausch Bullet points from the WPC Days 3-7 Hazards chart can be found at: https://www.wpc.ncep.noaa.gov/threats/threats.php - 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