Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 444 PM EST Wed Dec 28 2022 Valid 12Z Sun Jan 01 2023 - 12Z Thu Jan 05 2023 ...Major Storm to produce a New Year's Weekend Heavy Precipitation/High Wind Threat for the Upper Aleutians, Alaskan Peninsula/Kodiak Island, and coastal Southcentral and Southeast 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. While detail issues remain, they appear smaller than yesterday. A compromise approach of the deterministic guidance was used early, before transitioning to a split between the deterministic and ensemble means late, which is reflected in the AK 500 hPa heights, winds, pressures/fronts, and QPF. The other grids are more heavily influenced by the 19z NBM. ...Weather Impacts... While the interior will see relatively quiet weather and cold yet above average temperatures as upper-level ridging remains in place, a deep surface low is forecast to move into the western Gulf of Alaska near the Alaskan Peninsula on Sunday and linger through at least the first half of the forecast period before elongating into surface trough with time, both at the surface and aloft. 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 of southern AK. The highest chances for precipitation will shift from west to east from Saturday through Monday. Precipitation will likely linger into Tuesday, though does not look to be as heavy as moisture flow from the Pacific begins to dwindle. Strong, gusty winds are also expected with the tight pressure gradient between the surface low and inland ridging from the Alaskan Peninsula east through Southcentral and into the Panhandle, as well as portions of the Aleutians. These winds should weaken in tandem with the low pressure system over the forecast period. Another low approaches the Aleutians mid next week, but for the moment, appears to be a bit weaker. 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 the Alaska Panhandle and mainland Alaska, 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