Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 552 PM EST Mon Feb 24 2020 Valid 12Z Fri Feb 28 2020 - 12Z Tue Mar 03 2020 After getting a better handle on the large scale flow pattern across Alaska during the extended period, guidance continues to struggle with some of the details of individual systems. An upper-level high across eastern Siberia will allow for increasing influence from arctic shortwave energy across much of mainland Alaska, with another round of very cold temperatures likely. Farther south, a very active North Pacific storm track will persist across the Aleutians, with the potential for a deep surface low to move into the southern Bering Sea by the weekend. Models/ensemble show general consensus that a rapidly deepening low pressure system should approach the Aleutians and move into the southern Bering Sea Fri-Sat, potentially bringing high winds to portions of the Aleutians and the Alaska Peninsula. Models show some disagreement on the precise track/timing of this feature, but overall broad agreement on the deep nature of the system. The ECMWF seemed to be the solution most well-centered within the ensemble spread, and thus was weighted heavily in the forecast during days 4-5 (Fri-Sat) along with a smaller component of ECENS/GEFS ensemble means. By Sun the system is forecast to begin moving eastward across the Alaska Peninsula and southern mainland Alaska, with model spread gradually increasing. The system is expected to bring a period of widespread snow to the Alaska Peninsula and much of southern mainland Alaska, with rain across the Aleutians. There was some signal in the guidance of another similar (perhaps not quite as deep) low pressure system approaching the Aleutians by next Tue, although spread was quite high surrounding this feature, and confidence in the specifics low. Weighting of ensemble means was gradually increased during the day 6-8 (Sun-Tue) time period to account for the increasing spread. 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 Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu, Feb 27. - High winds across portions of mainland Alaska and the Aleutians, Sat-Sun, Feb 29-Mar 1. - Much below normal temperatures across portions of mainland Alaska, Thu-Mon, Feb 27-Mar 2. - Much below normal temperatures across portions of far northern mainland Alaska, Thu-Fri, Feb 27-Feb 28. 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