Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 554 PM EST Fri Nov 22 2019 Valid 12Z Tue Nov 26 2019 - 12Z Sat Nov 30 2019 ...Major Bering Sea Storm Early Next Week Threatens West/Northwest/Interior Alaska... ...Guidance/Uncertainty Assessment... The 12 UTC GFS/ECMWF offer excellent forecast clustering with each other and the 12 UTC GEFS mean and 00 UTC ECMWF ensemble means next Tuesday-Thursday. A blended deterministic model solution offers a good forecast starting point with above normal predictability. The models are still generally in line with the larger flow evolution, but offer a bit more variance days 7/8. Prefer an ensemble based solution for these longer time frames. Applied heavy weighting to ECMWF ensembles that better match with the 12 UTC GFS/ECMWF. ...Weather/Hazard Highlilghts... A robust Bering Sea system will lift in energetic flow to the Bering Strait/Arctic and northwest Alaska Tuesday-Thursday of next week. Lead flow will slam inland with vigor through western/northwest Alaska then the North Slope. Guidance is in good agreement with this hazardous storm, bolstering forecast confidence. The unusually well supported storm and organized frontal system will bring a leading surge of strong southerly winds to the west/northwest coast of Alaska, including areas where near-offshore ice is still forming. This area was depicted on the WPC day 3-7 hazards chart again for the wind/wave/precipitation threat. There is an increasing guidance signal for another deep low to work up into the Bering Sea again later next week, mainly as a maritime risk this period. Meanwhile, an uncertain Pacific evolution is slowly coming into better agreement, with a closed low south of the Aleutians lifting north-northeastward and gradually weakening, but still supporting a weather focusing surface low/frontal system up into the Gulf of Alaska. This complex system may tap anomalously deep moisture to fuel some potentially heavy precipitation into the Alaskan southern/southeast tier later next week. Schichtel 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 - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Wed-Fri, Nov 27-Nov 29. - Heavy precipitation across portions of mainland Alaska, Tue-Thu, Nov 26-Nov 28. - Heavy snow across portions of mainland Alaska, Tue-Thu, Nov 26-Nov 28. - High winds across portions of mainland Alaska, Tue-Wed, Nov 26-Nov 27. - High significant wave heights for coastal portions of mainland Alaska, Tue-Wed, Nov 26-Nov 27. 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