Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 606 PM EST Sun Mar 07 2021 Valid 12Z Thu Mar 11 2021 - 12Z Mon Mar 15 2021 ...Overview and Guidance/Uncertainty Assessment... Progressive quasi-zonal flow will trend toward increased troughing in the Bering Sea, downstream of elongated upper ridging from eastern Asia (China/Mongolia) into the western Pacific Ocean. Lead system out of the northeastern Pacific remains tough to pin down details, owing to continued differences in timing/strength of northern and southern stream influences. After a quicker/less-phased shift yesterday, consensus drifted back toward a bit slower but still not quite robust system. ECMWF ensembles remained slowest along with the Canadian, hanging back a deep upper low well south of the Gulf. Again favored the 12Z ECMWF with some influence from the GFS and then GFS parallel as the operational version was quickest. This stayed toward the middle of the spread as a continued hedge against future model shifts. To the west, deepening troughing will favor increased meridional flow across the Aleutians and then into western areas of the Mainland as a system congeals from northern and southern streams into a stretched frontal system with the parent low well northwest over northeastern Russia. With differences in the evolution (speed of southern system into the in-situ front), opted to rely on the rather agreeable ensemble means (ECMWF EPS and GEFS mean). Amplifying trough/ridge pattern may slow the system into western Alaska and the Gulf next weekend/early next week, but downstream ridging does not look that impressive just yet. ...Weather/Hazards Highlights... High pressure over northwestern areas will slowly move through the Interior and Southcentral Thu-Sat, supporting colder temperatures 10-15 degrees below normal. The colder temperatures will make its way southeastward as the surface high slips into northwestern Canada/Yukon. Lead Gulf system will track toward the central/southern Panhandle, focusing the precipitation there as the front moves into British Columbia late Fri. Heaviest amounts per the in-house bias-corrected ensemble QPF should stay south of Juneau. Next system in the Bering will bring windy conditions and some rain/snow to the islands as the parent low stays well to the northwest. Milder temperatures will precede the Bering system on southerly flow from west to east next weekend, suggesting a transition to rain for some areas. Wave along the front is forecast to redevelop into the Gulf, perhaps enhancing the rain/snow over the AKPen/southwest areas into Kodiak. 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 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