Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 415 PM EST Tue Dec 27 2022 Valid 12Z Sat Dec 31 2022 - 12Z Wed Jan 04 2023 ...Major Storm to produce a New Year's Weekend Heavy Precipitation/High Wind Threat for the Alaskan Peninsula/Kodiak Island and coastal Southcentral Alaska... ...Guidance/Predictability Assessment... Models and especially ensemble means offer a reasonably similar mid-larger scale pattern evolution over medium range time scales, bolstering forecast confidence. n Upper troughing extends from Siberia through southwest AK into the northeast Pacific/Gulf of AK. Ridging remains in place across eastern AK. However, models still show ample differences with embedded smaller scale weather systems/features. There remains a quite favorable signal to ring in 2023 with development and track of a deep low/storm to the south of the Aleutians and towards the AK Panhandle. The guidance mostly, outside of the 00z/12z ECMWF runs, favors a system wobbling or looping quite close to there, while the ECMWF continues to swing it wide to the east, a bit east of its own ensemble mean. Otherwise, there are detail issues with various pieces of guidance which argue for a compromise approach early, and a more ensemble mean approach late, which is reflected in the AK 500 hPa heights, winds, and pressures/fronts. The other grids are more heavily influenced by the 19z NBM. ...Weather Impacts... While the interior will see relatively quiet weather and above average temperatures as upper-level ridging remains in place, a deep surface low is forecast to move into the western Gulf of Alaska and Alaskan Panhandle early in the period. Warmer, moist air will flow northward ahead of an occluding front leading to the chance for multiple days of heavy rain at lower elevations near the coast and heavy snow at higher elevations in the mountains. The highest chances for precipitation will likely shift from west to east across southern AK from Saturday through Monday. Strong, gusty winds are also expected with the tight pressure gradient near and ahead of the surface low for the Alaskan Panhandle and South Central, and like the heavy precipitation, shifting from western portions of the area on Saturday to the east on Sunday. There is a signal in the guidance for another low pressure system to follow late in the period, which could wetten the western Aleutians next Tuesday into Wednesday, though it's unclear how much at this juncture. Putnam/Roth Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Mon, Dec 31-Jan 2. - High winds across portions of mainland Alaska and the Aleutians, Sat-Sun, Dec 31-Jan 1. Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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