Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 254 PM EST Sat Feb 02 2019 Valid 12Z Wed Feb 06 2019 - 12Z Sun Feb 10 2019 Amplified flow is expected to persist from the North Pacific to Alaska during the extended period. A mean trough will persist across the 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. Models show good consensus that a mature low pressure system will be crossing the Bering Sea on Wed. Another low pressure system should be weakening across the Gulf of Alaska on Wed as it moves into anticyclonic mid/upper-level flow on the northern periphery of the ridge. Deterministic/ensemble solutions were well clustered with these systems. A blend of the ECMWF and GFS served as a basis for the forecast starting on day 4 (Wed) and continuing into day 5 (Thu). During days 6-8 (Fri-Sun) models/ensembles continued to generally show good large scale agreement, but with some important differences emerging by late next week into next weekend. Another vigorous shortwave should approach the Aleutians/Bering Sea by Fri along with an associated deepening low pressure system. Solutions differ as to the intensity of this feature and the exact track, although the ECMWF has been the most consistent and is closest to the consensus of ensemble means. The GFS has been consistent in quickly breaking down the upper ridge by next Sat-Sun as a strong north Pacific jet moves into the region, while the ECMWF has consistently been slower to break the ridge down. Ensembles (including the GEFS) suggest that the GFS may be a bit too quick to break down the ridge, so preferred to at least lean toward the ECMWF and ensemble means by days 6-8, with some modest inclusion of the deterministic GFS to temper the ridge strength a bit. 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