Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 327 PM EDT Thu Apr 25 2019 Valid 12Z Mon Apr 29 2019 - 12Z Fri May 03 2019 During the first half of the week there is relative agreement on an amplified pattern as mainland ridging aloft builds northward and troughing prevails over the Bering Sea. At the surface, gradually weakening high pressure should prevail over the eastern 2/3 of the mainland and northeastern Pacific while strong low pressure tracks northward over the western Bering. Flow to the west of the surface high and wavy front extending from the Bering low will provide some precipitation enhancement over the Alaska Peninsula and eastern Aleutians. By mid-late week there is a decent signal for an upper high to close off and progress northward to some degree--perhaps leaving some type of weakness over the mainland--while mean troughing should exist between eastern Asia into the Bering but with a lot of uncertain details. Flow around a Canadian upper low may push a front into the Panhandle and eastern mainland. For the mainland ridge aloft there has been a rapid trend toward farther north progression of the closed high which ECMWF/GFS runs and their means lift into the Arctic. Over the past day the ECMWF/ECMWF mean have generally led this trend but there are still minority solutions like the 00Z CMC/NAVGEM which do not lift the upper high into the Arctic. The 12Z GFS adjusted more to the ECMWF (and in fact exceeded it for a time around Wed) but the ongoing spread favored a compromise approach among the 06Z GFS/FV3 GFS, 00Z ECMWF, and 06Z GEFS/00Z ECMWF means to provide a nudge from continuity while awaiting confirmation of recent significant trends. Even with the differences in specifics aloft among the GFS/ECMWF runs and their means, there is a decent consensus at the surface toward high pressure building over the Arctic relatively lower pressure over the southern mainland. Farther west a compromise (by way of the aforementioned model/mean cluster) accounts for slower ECMWF trends closer to the GFS with the Mon-Wed low over the Bering. Otherwise details from eastern Asia across the Bering are not especially clear aside from the area tending to be under mean troughing aloft. At the very least there is a decent consensus suggesting that Bering/Aleutians energy will not be as quick to reach the Gulf of Alaska as depicted in the 12Z GFS. Consistent with emphasizing operational model detail early and accounting for increasing spread/uncertainty with time, the forecast started with 80 percent total weight of 06Z GFS/FV3 GFS and 00Z ECMWF guidance on day 4 Mon and then gradually transitioned toward 70 percent total 06Z GEFS/00Z ECMWF ensemble weight by day 8 Fri. Rausch Bullet points from the WPC Days 3-7 Hazards chart can be found at: https://www.wpc.ncep.noaa.gov/threats/threats.php - High winds across portions of the Aleutians, Sun-Mon, Apr 28-Apr 29. 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