Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 318 PM EDT Sat Sep 07 2019 Valid 12Z Wed Sep 11 2019 - 12Z Sun Sep 15 2019 A good majority of model and ensemble guidance agrees fairly well that deep Bering Sea low pressure and associated upper low/trough should gradually weaken by next Sat-Sun as the system reaches the mainland and vicinity. The initial surface low reflects the extratropical evolution of Typhoon Lingling. This system should produce a broad area of fairly strong winds while leading flow/moisture will likely focus significant precipitation across the extreme southern mainland and into the Panhandle. The most prominent detail question early in the period involves Typhoon Faxai (currently to the southeast of Lingling)--specifically if/when/how it interacts with the initial Bering low/trailing front. Thus far recent and latest operational model runs have varied with no clear high-probability scenario yet apparent. An operational model blend including the 00-06Z GFS and 00Z ECMWF/UKMET provides the best starting point for the manual forecast, indicating some potential for merging like the 00Z ECMWF/UKMET but a bit less aggressively. The main theme is to depict a deeper Bering system than shown in the ensemble means. Note that the 00Z CMC begins to stray north of consensus with the Bering system and in addition pulls the Wed-Thu system over the northeastern Pacific well southward of consensus, so that model could not be used. By the latter half of the period upstream shortwave energy may produce a surface wave from the North Pacific into the Gulf of Alaska but again clustering and continuity among the operational runs have not been that great and ensemble members are diverse enough for a North Pacific wave not to show up in the means. Meanwhile solutions gradually diverge for the exact position of the Bering low that reaches the western coast of the mainland. Trending the forecast increasingly toward the agreeable ensemble means with time provides the best starting point, with day 7 Sat still containing enough operational guidance to provide a hint of waviness tracking to the south of the eastern Aleutians/Alaska Peninsula. Low pressure over the Gulf of Alaska by day 8 Sun would have support from some combination of North Pacific shortwave energy and/or energy approaching from the eastern Bering. The overall day 8 pattern has been consistent over multiple GEFS/ECMWF mean runs so confidence in having a Gulf low by day 8 is higher than the specifics of how it reaches that position. Rausch Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php 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