Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 639 PM EST Thu Jan 16 2020 Valid 12Z Mon Jan 20 2020 - 12Z Fri Jan 24 2020 The large scale pattern across Alaska during the extended forecast period is forecast to be strikingly different than that seen during the short range. A mean trough/upper low is forecast to develop/persist across the Arctic Ocean north of Alaska and Siberia through the extended forecast period, with an active storm track across the North Pacific, generally south of the Aleutians, and into the Gulf of Alaska, and upper ridging shifting eastward into west central Canada. Throughout much of the extended forecast period, the 12Z GFS seemed to be the piece of deterministic guidance most well-centered within the spread of ensemble members. The first such system is forecast to be moving north across the Gulf of Alaska on Mon, with another deeper system passing south of the Aleutians Mon into Tue. For the latter of the two, the ECMWF was quite a bit slower even when compared to the ECENS mean (which was closer to the GFS). This system is forecast to move into the Gulf of Alaska on Wed, with yet another low following a similar track in its wake, passing south of the Aleutians on Wed. Guidance generally agrees on a somewhat slower progression for this system as it deepens and becomes more wrapped up. As with the prior systems the GFS was reasonably close to the ensemble means. Farther north, a stream of relatively weak upper-level shortwaves are forecast to progress across the Interior and the North Slope as energy traverses around the Arctic trough/upper low. Models showed some inconsistencies with these features among each other as well as run to run, but the GFS was reasonably representative of the ensemble consensus here as well. Based on the described factors, the WPC forecast was based heavily on the 12Z GFS, with increasing weight placed on GEFS/ECENS ensemble means going farther out in time. The general agreement of the GFS with the ensemble means allowed for its used to add detail to features/systems through the end of the forecast period. Ryan 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 - Heavy precipitation across portions of the Alaska Panhandle, Sun-Tue, Jan 19-Jan 21. - Much below normal temperatures across portions of mainland Alaska, Sun-Mon, Jan 19-Jan 20. 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