Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 535 PM EST Sat Dec 21 2019 Valid 12Z Wed Dec 25 2019 - 12Z Sun Dec 29 2019 ...Below Average Temperatures for much of Mainland Alaska... ...Strong storms to track near the Aleutians and the Southern/Southeast Mainland... ...Guidance/Uncertainty Assessment... Guidance is well clustered days 4/5 (Christmas/Day After Christmas), bolstering forecast confidence. A composite blend of the 12 UTC GFS/ECMWF and GEFS/NAEFS/ECMWF ensemble means seems to provide a solid starting point for production of the WPC Alaskan medium range product suite along with input from the 19 UTC National Blend of Models. Model forecast spread and run to run continuity variance becomes more robust days 6-8, especially with offshore systems. However, the preferred 12 UTC GEFS/NAEFS/ECMWF ensembles remain fairly well clustered and seem to offer reasonable predictability that coupled with the NBM maintains decent continuity. ...Weather/Hazards Highlights... A lingering and unsettling mean upper trough centered over the interior with have cold lower atmospheric air underneath in a pattern with below normal temperatures for much of the mainland next week. A strong storm track underneath will feature two main systems. A lead low and frontal system is progged to track near the Aleutians and Alaskan Penisula/Kodiak Island onward over the far northern Gulf of Alaska near southern/southeast Alaska. This will offer a maritime risk of high wind/waves along with a focus for heavy precipitation that will also feed inland, mainly into coastal areas and favored terrain of southern/southeast Alaska Christmas into Friday, with lingering activity into next weekend. Meanwhile, there is also a growing signal supporting another significant/deep low back upstream than works northward to the Aleutians next weekend that will also offer a maritime and onshore threat for the region, with heavy seas/winds also feeding up into the Bering Sea. 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 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