Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 553 PM EST Thu Dec 26 2019 Valid 12Z Mon Dec 30 2019 - 12Z Fri Jan 03 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 as heights relax a bit. The models/ensembles showed good agreement overall with the synoptic pattern but still differed on system timing/track/strength with less than desirable run-to-run continuity. Once again, the 12Z GFS did not cluster well with the 12Z ECMWF/Canadian/UKMET with the lead system into Southwestern Alaska. However, the 12Z GFS run from 12/25 (which was more or less on its own then) was closer to today's consensus. With the latest guidance, it has become more of a timing issue rather than track issue, with the GFS being about 24 hrs slower than the rest. Opted again to rely on the larger cluster of solutions including the ECMWF ensemble mean. Thereafter, by Wed 1/1, the GFS developed a sfc wave on a front south of 45N and moved it into the Gulf. The ECMWF/Canadian (and UKMET through 144hrs) did not, similar to continuity. Preferred to withhold this system for now. By next Thu/Fri, system should push through the Aleutians from the west as perhaps another shot of colder air circulates around the weakening upper low over Southwest Alaska or Southcentral. Cold air will moderate slightly early next week from a cold weekend but remain below average. This may be reinforced later next week. Rainfall (and snowfall) will be quite heavy across parts of coastal Southcentral (southeastern Kenai to Prince William Sound) eastward to the Panhandle given the storm track of the lead system, with associated high winds possible. Precipitation should decrease with time with weaker systems through the area, assuming the Gulf system around Wednesday does not materialize. 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, Sun-Tue, Dec 29-Dec 31 and Wed-Thu, Jan 1-Jan 2. - High winds across portions of mainland Alaska, Mon-Tue, Dec 30-Dec 31. - Much below normal temperatures across portions of mainland Alaska, Sun, 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