Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 611 PM EST Fri Dec 22 2023 Valid 12Z Tue Dec 26 2023 - 12Z Sat Dec 30 2023 ...General Overview... A deep layered mid-upper level low will be anchored in place across the eastern Bering and western mainland Alaska for the beginning to middle of next week, accompanied by frigid conditions, and a surface low reaching the southeastern mainland coast followed by steady weakening. Going into the end of the week, the Bering upper low is likely to retrograde some to the west with a new upper low/surface low taking shape near the Aleutians, and surface high pressure governing the weather pattern over the Interior. A well organized low pressure system is likely to evolve just south of the Aleutians by next weekend as the upper level pattern becomes more amplified. ...Guidance Evaluation/Preferences... The 12Z model guidance suite has a reasonably good overall depiction of the weather pattern across the Alaska domain for the Tuesday to Wednesday time period, although there are already noteworthy timing differences with the low crossing the eastern Gulf (ECMWF faster and the CMC/GFS slower). Big timing differences continue across the eastern Gulf going into Thursday with the next storm system, with the GFS well to the south. Looking ahead to Friday and Saturday with the next big Bering Sea storm system, the models agree that a well organized low will evolve, but differ on whether it would be one main low or a pair of lows, but for simplicity the progs will denote a single main low for now until model details become clearer. The WPC fronts/pressures was primarily based on a nearly multi-deterministic model blend on Tuesday, and gradually increasing the percentage of the ensemble means to about 50-60% by the end of the forecast period. ...Weather/Hazards Highlights... Heavy snow is expected from Prince William Sound eastward to the St. Elias Mountains on Tuesday, along with rain near the immediate coast, associated with an influx of moisture from the Pacific as a surface low moves in from the eastern Gulf. There will likely be lingering moderate to locally heavy precipitation for the southeast Panhandle region going into Wednesday and Thursday with continued onshore flow. Another round of organized moderate to heavy precipitation is looking more probable for portions of the Alaska Peninsula and into the Kenai Peninsula and Chugach Mountains to close out the work week. Breezy to windy conditions are also expected across the Aleutians for the Thursday to Saturday time period with a strong surface low in the vicinity of the islands. The deep closed low across the western part of the state will promote frigid temperatures for the Alaska Peninsula and western Mainland for the first half of next week, mainly northwest of the Alaska Range where some overnight lows could bottom out in the -30s! There will likely be a temperature dichotomy in place, as southwesterly flow should lead to above normal temperatures on average for eastern portions of the mainland, lingering longest in the northeastern part of the state through about Wednesday. There should be a welcomed return to moderating temperatures by Friday and especially into next weekend with a pattern change developing, and some above average readings are likely to be realized. 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