Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 556 PM EST Wed Dec 25 2019 Valid 12Z Sun Dec 29 2019 - 12Z Thu Jan 02 2020 Upper troughing will dominate the southern portion of mainland Alaska next week in between ridging over eastern Russia and off the coast of Washington/British Columbia. The pattern will slowly move eastward by the end of the period, with the trough axis nearing 150W and ridging moving into the Bering. The models/ensembles showed good agreement overall with the synoptic pattern but still differed on system timing/track/strength. Overall the 12Z GFS seemed to depart most from the otherwise reasonable consensus of the 12Z ECMWF/UKMET/Canadian with the lead system Sun-Tue. Did not favor taking any surface low across the AKPEN into Bristol Bay though there remain about a dozen or more ensemble members that do just that. However, trend in the guidance was to bring the surface low NNE into/through Cook Inlet rather than linger it just off the Kenai peninsula or south of Prince William Sound. This could bring in significant precipitation to coastal areas with southerly to southeasterly exposure. Reinforcing cold front may bring in another round of colder air as the upper trough axis moves eastward next Tue-Thu. Trended toward nearly all ensemble means by next Wed/Thu as the ECMWF/Canadian drifted well apart with the next system south of the Gulf -- either advancing it northeastward or stalling it in place. Either way, it appears it may stay south of the Panhandle underneath the weakening northern feature. Cold air will moderate slightly early next week but remain below average. This may be short-lived if the second surge spread eastward next Tue-Thu. Rainfall (and snowfall) will be quite heavy across parts of Southcentral to the Panhandle given the storm track of the lead system, with associated high winds possible. Future shifts in the track will determine the details of the forecast. 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, Sat-Tue, Dec 28-Dec 31. - High winds across portions of mainland Alaska, Mon-Tue, Dec 30-Dec 31. - Much below normal temperatures across portions of mainland Alaska, Sat-Sun, Dec 28-Dec 29. - High significant wave heights for coastal portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Dec 31-Jan 1. 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