Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 634 PM EST Sun Dec 31 2023 Valid 12Z Thu Jan 4 2024 - 12Z Mon Jan 8 2024 ***Multiple strong storms to bring windy conditions for the Arctic Coast, the Aleutians, and portions of the mainland*** ...General Overview... A powerful surface low is expected to cross the Aleutians on Wednesday, likely peaking in the 940s for pressure before entering Bristol Bay and the southern Bering Sea, and weakening going into the end of the week. Meanwhile, an arctic surface high is expected to be anchored in place several hundred miles north of the Arctic Coast, and this will create a very strong pressure gradient across the entire state, and therefore strong winds across the North Slope/Arctic Coast and the Aleutians and Alaska Peninsula. The active weather pattern continues going into next weekend with a second low pressure system becoming better organized and quickly deepening southwest of the central Aleutians by Friday, but this low is currently expected to track a little farther northwest than the first system. This storm is also expected to be impactful with high winds/seas. Looking even farther ahead to late next Monday into Tuesday, a potential third system may approach the Aleutians once again. ...Guidance Evaluation/Preferences... All of the deterministic guidance depicts a steady weakening of the first low pressure system over the eastern Bering for the end of the week. The 12Z GFS/CMC are stronger with a shortwave trough/low pivoting around the southern periphery of the main low across the Gulf on Friday compared to the ECMWF. 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 the CMC is to the west of the model consensus with this low as it tracks northeastward, so it was weighted less in the forecast blend for the second half of the forecast period. The use of the ensemble means increased to about 40% by next Sunday-Monday. ...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. The coldest temperatures are expected for the more sheltered Interior valley locations. 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