Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 555 PM EST Thu Jan 09 2020 Valid 12Z Mon Jan 13 2020 - 12Z Fri Jan 17 2020 ...Guidance/Predictability Assessment... The latest runs of the 12z deterministic guidance show fairly good agreement on a weakening surface low crossing the Bering Straights Monday up into the Arctic Ocean early next week. Farther south, a frontal wave with weak low pressure embedded within the frontal circulation persists over the southern Gulf of Alaska by Tuesday and into Wednesday, and merges with low pressure moving further south in the northern Pacific by Wed 15 Jan. By next Tue, a large cyclone and frontal system move slowly east into the western Bering Sea. The trailing front crosses the Aleutians, with waves of low pressure possible developing along the front and moving north across the Aleutians. The big changes on the 12z ECMWF make the forecast challenging, with low confidence on the magnitude of the run to run change in the operational ECMWF forecast from the 00-12z runs. The 12z ECMWF has better continuity with the low developing and located just south of the lower Aleutians next Fri 17 Jan., as the 12z Canadian cyclone position is close by, resulting in good overlap among the 2 ECMWF operational runs/ECMWF ensemble Mean, and Canadian global cyclone positions. To mitigate the various model solutions, for the 500 mb and sfc forecast mass field forecasts, a blend of the 12z Canadian, GFS, UKMET. and 00z ECMWF/ECMWF Ensemble Mean solutions was used for days 4-8. ...Weather/Hazards Highlights... Much of AK south of the north slope will have lingering much below normal temperatures expected days 4-5 over the eastern Interior/Southeast and Panhandle region as arctic high pressure continues in place. Temperatures across some of the more sheltered valleys in the eastern Interior may approach 50 below Monday morning. On next Thu-Fri, marine modified air starts moving onshore in most solutions from the Bering Sea and north Pacific into western Alaska, so the air mass starts to moderate. No major heavy precipitation events are expected through the middle of next week. The next surface cyclone crossing the Aleutians/nearby waters may bring a period of gusty winds and precipitation during the middle of next week. Petersen 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: - Much below normal temperatures across portions of mainland Alaska, Sun, Jan 12. - Much below normal temperatures across portions of the Alaska Panhandle, Sun-Tue, Jan 12-Jan 14. 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