Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 251 PM EST Sun Feb 03 2019 Valid 12Z Thu Feb 07 2019 - 12Z Mon Feb 11 2019 Amplified flow is expected to persist from the North Pacific to Alaska during the extended period. A mean trough will persist across the western Aleutians and portions of the Bering Sea, with downstream ridging from the Gulf of Alaska north into mainland Alaska. A number of systems will rotate through the mean Bering trough during the period, and models/ensembles showed relatively good consensus, especially during the first half of the extended period. One frontal system should move from the eastern Bering Sea into mainland Alaska and the Kenai Peninsula as it weakens Thu-Fri, with a second system following fairly closely behind, entering the western Bering Sea late Fri into Sat. The ECMWF has shown much more run-to-run consistency with this second system (relative to the GFS) and also is generally close to the ensemble means. The GFS also quickly digs the shortwave east into the ridge, toward the Gulf of Alaska, while the ECMWF keeps the ridge stronger and takes the shortwave energy farther north toward mainland Alaska. From Sat-Mon the GFS has continued to break the upper ridge down more quickly than the ECMWF allowing progressive north Pacific flow to take hold. The 12Z GFS has backed off of this somewhat, while the CMC has come around to a more ECMWF-like solution holding the ridge stronger for longer. A stronger ridge has continued to have more ensemble support so this will continue to be the preference. This would keep the flow more amplified and allow another potentially deep low pressure system in the Bering Sea by early next week. The ridge could begin to weaken some by early next week (as shown by the ECMWF), allowing more progressive flow to take hold, although ensemble means suggest that this could still be too quick, with the ECENS keeping a ridge axis in place through day 8. With these considerations in mine, the WPC forecast was initially based on an ECMWF/GFS blend on day 4 (Thu), with a transition to majority ECMWF/ECENS mean weighting from day 6 (Sat) through the duration of the forecast period. Ryan 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