Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 657 PM EST Sat Dec 30 2023 Valid 12Z Wed Jan 3 2024 - 12Z Sun Jan 7 2024 ***Windy conditions for the Arctic Coast, the Aleutians, and portions of the mainland*** ...General Overview... A powerful surface low is expected to develop over the North Pacific and then cross the Aleutians going into the middle of the week, likely peaking near 950mb or even lower by Wednesday morning as the circulation enters Bristol Bay and the southern Bering Sea. Meanwhile, an arctic surface high is expected to be anchored in place several hundred miles north of the Arctic Coast, and this will create an impressive pressure gradient across the entire state and strong winds across much of the mainland and especially the Aleutians and Alaska Peninsula. This low gradually weakens by the end of the week across the western mainland, followed by a second low pressure system becoming better organized just south of the central Aleutians by Friday, currently expected to track farther northwest that the first system. ...Guidance Evaluation/Preferences... All of the deterministic guidance continues to depict a very strong low pressure system in the general vicinity of Bristol Bay for the middle of the week. The 12Z GFS has trended closer to the model consensus compared to its more eastern solution from yesterday, so this solution was weighted more in the forecast blend for fronts and pressures, along with the 12Z ECMWF. The CMC indicates a slightly more western track with the low compared to the GFS/ECMWF, but still within the realm of possibility. For the second storm system heading towards the Aleutians/Bering next weekend, the models have consolidated quite well and are now suggesting the potential for a sub-960 mb low by 12Z Saturday over the southern Bering, but there is more model spread across the Gulf where shortwave energy pivoting around the main vortex has some timing differences. The use of the ensemble means increased to about 40% by next Sunday. ...Weather/Hazards Highlights... The heaviest precipitation is expected to occur on Wednesday from the eastern Alaska Peninsula to the Chugach Mountains, with up to a few inches of QPF expected across the favored terrain. The onshore flow abates going into Thursday and Friday and thus a reduction of precipitation is expected to close out the work week. However, a renewed round of enhanced precipitation is likely by next weekend as southerly flow increases ahead of the next Bering Sea low. Widespread gale to occasional storm-force winds are expected across much of the Arctic Coast and adjacent portions of the North Slope, Kotzebue Sound, Norton Sound, the Aleutians, and the usual favored locations in southern Alaska, all driven by a potential 90-100 mb pressure gradient between the Arctic Ocean and the Aleutians/southern Bering Sea on Wednesday! This storm will also be accompanied by wave/swell threats across the Bering and North Pacific, and ground blizzard conditions for the Arctic Coast region. Temperatures across western and southern Alaska should warm to above average levels while colder weather across the North Slope and eastern interior persists longer. 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