Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 635 PM EST Thu Nov 30 2023 Valid 12Z Mon Dec 04 2023 - 12Z Fri Dec 08 2023 ...Overview... Strong Pacific jet across most of the basin will transition toward a resurgence off eastern Asia in between building subtropical ridging and an anticyclone over Siberia by later next week. This will favor split flow starting just west of the Dateline, allowing much more northern stream energy to move into the mainland from the Bering. Before that transition, a trough in the northeast Pacific will lift through the Gulf of Alaska carrying a progressive but modest system through the Panhandle. ...Guidance Evaluation and Preferences... Models and ensembles have mostly converged toward a common solution in the first few days of the forecast period, and the 12Z GFS/ECMWF/Canadian formed a reasonable cluster near the ensemble mean consensus with the low wrapping up into the Gulf of Alaska Tuesday afternoon before meandering there for a couple more days. By around Wednesday, the ensembles showed considerable uncertainty/spread out of northeastern Russia in response to an upstream amplifying trough/ridge couplet over Siberia/Kamchatka, respectively, and the speed of an ejecting shortwave across the Bering. The overall multi-ensemble trend has been quicker, but the ECMWF ensembles were much quicker than the GEFS/GEPS to bring in the upper low into the western Mainland. Though the quicker trend may favor the ECMWF ensembles, opted to rely on a middle ground solution since this was already a sizable change from the forecast 24 hrs ago. Quick look at the latest 12Z ECMWF EPS shows a bit slower solution, giving credence to the middle ground solution for now. By next Thu/Fri, ensembles actually showed better agreement on longwave troughing settling into western/southwestern Alaska, carrying the northern stream surface front into the Gulf. There are some indications that southern stream energy may try to sneak northeastward into the east side of the trough next Friday, but there remains lots of time to sort of details. A blend of the 12Z GFS/Canadian/ECMWF with the ensemble means served as a good starting point to the second half of the forecast. ...Weather/Hazards Highlights... Much of significant precipitation will be associated with the lead Gulf system for the Panhandle/Southeastern Alaska early in the week. The most concentrated moisture flux will be centered near and south of the triple point, generally over Hadai Gwaii and southwestern B.C., but modest rain/snow is expected for the Panhandle. NBM probabilities show low chances of exceeding 3 inches of rain in 24-48 hours for at least the lower elevations, so no hazard areas were drawn again today. It will be rather breezy around the deep low, though most of the highest winds may stay offshore or just skirt the western coast of the Panhandle. By midweek, the northern stream system will being some rain and mostly snow to the Aleutians and western areas but generally on the lighter side. Light snow accumulations are expected over northern areas in the interior to the Brooks Range. Temperatures will start milder than average over most locations, trending colder with time, especially over southwestern areas into Southcentral by later next week. Fracasso Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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