Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 653 PM EST Wed Jan 1 2025 Valid 12Z Sun Jan 5 2025 - 12Z Thu Jan 9 2025 ***Heavy precipitation expected early next week for the eastern portion of the Alaska Peninsula to the southern mainland coast*** ...Overview with Guidance Evaluation and Preferences... The forecast period begins on Sunday with an upper trough draped across the north-central Alaska mainland, and a closed upper high over eastern Siberia and a building ridge axis near British Columbia and the southeast Panhandle region. Meanwhile, a broad upper level low situated just south of the central Aleutians should be anchored in place through early next week, and multiple low pressure systems are forecast to pivot around this and cross the Gulf and affect the southern mainland, with the strongest system expected to arrive on Monday with high winds and heavy precipitation from the Alaska Peninsula to the Kenai Peninsula. A positive PNA pattern develops with a major western Canada upper ridge next week, and a general trough remains in place across the Bering into the western Gulf. The model guidance is initially in good overall synoptic scale agreement across the domain Sunday, with some timing differences in the arrival of shortwave perturbations across the Gulf. With the main event arriving Monday, the ECMWF is the fastest in bringing the low to the Alaska Peninsula, and the GFS/CMC arriving about 12-18 hours later on Monday, with the GFS remaining the strongest solution. Going into Tuesday, the CMC brings that low farther east across southwest mainland Alaska, whereas the GFS/ECMWF favor a track reaching the eastern Bering by Tuesday night. For Wednesday into Thursday, another low pressure system may follow right behind it, with the GFS portraying this scenario more than the ECMWF, and the CMC is slower with that same system. The ensemble means were gradually increased to about half by end of the forecast period to account for increasing timing and intensity differences. ...Weather/Hazards Highlights... Unsettled weather conditions are expected for much of southern mainland Alaska and the coastal terrain for the upcoming weekend and into early next week, with a more active storm track from the Gulf. A couple of weaker disturbances are expected to lift north across the Gulf through Sunday with periods of mainly moderate rain and mountain snow. However, a considerably stronger storm system gets better organized over the southern Gulf and then lifts northward to affect the Alaska Peninsula and points east to the St. Elias Mountains for much of Monday and into Monday night. Some model solutions are quite intense with pressures well under 970mb, and this would equate to a high wind threat across the maritime zones and near the coast and the coastal mountains, with storm force winds likely. With strong onshore flow and orographic forcing, several inches of rain near the coast and multiple feet of snow is anticipated through early Tuesday. This event may be followed by another storm from the Gulf, although probably weaker than the Monday storm. Bitterly cold conditions across much of the Interior this weekend should slowly moderate going into the beginning of the week, mainly in response to increasing southerly low level flow from the Gulf and the building upper ridge over British Columbia and the Yukon. Conditions should be near climatology for early January by Tuesday for the Interior, whereas much of the region south of the Alaska Range should enjoy above average temperatures lasting through next Thursday. The moderation trend is not expected to make it north of the Brooks Range however, with frigid conditions continuing across the North Slope region. Hamrick 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