Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 642 PM EST Mon Feb 01 2021 Valid 12Z Fri Feb 05 2021 - 12Z Tue Feb 09 2021 ...Overview and Guidance/Uncertainty Assessment... Upper ridging between Siberia and the North Pole will slowly spill over into the Canadian Archipelago, allowing a closed low initially near Banks Island to migrate westward toward the North Slope/Beaufort Sea. Farther south, ridging over the northeastern Pacific/Gulf of Alaska will weaken with time, opening up the flow along 50N out of the northern Pacific. After a sizable change in the guidance yesterday, the models/ensembles had a better handle on the forecast for at least the Fri-Sun period. Used a blend of the 12Z GFS/Canadian/ECMWF and the GEFS/ECMWF ensembles which take an initial system nearing the central/eastern Aleutians Friday eastward atop the ridge as it collapses to the southeast. By Sunday, GFS started to become rather aggressive with height falls into northeastern Alaska to the southwest of the ensemble consensus (closer to the ECMWF at least for Sunday). After Sunday, deterministic models diverged rather quickly out of the north central Pacific in the quasi-zonal flow ahead of a deepening upper low off Kamchatka, suggesting a full use of the ensembles for next Mon-Tue to mitigate errors in the timing of a system into the Gulf around next Monday and into the Bering next Tuesday. ...Weather/Hazards Highlights... Northerly to northeasterly track of the lead system out of the mid-latitudes Friday will bring a modest surge of moisture into the eastern Aleutians and along the coast of Southcentral Alaska as it translates into the Gulf. Some locally heavy snow and coastal rain are possible, expanding into at least the northern Panhandle ahead of the warm front. Thereafter, precipitation will generally be light except around the system Sun-Mon from the Aleutians to the Gulf which may be enhanced a bit around the surface low. Temperatures will initially be near to above average over much of Southcentral as the system moves through. Below normal temperatures over northeastern areas will expand southwestward as heights lower out of northwestern Canada this weekend. Much of the state may see below normal temperatures by next week by about 5-15 degrees. Fracasso 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, Fri-Sat, Feb 5-Feb 6. 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