Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 656 PM EST Tue Mar 05 2024 Valid 12Z Sat Mar 09 2024 - 12Z Wed Mar 13 2024 ...General Overview... An upper level trough and accompanying cold front is forecast to extend southward from the Arctic into the weekend, resulting in a return to considerably colder temperatures for much of the mainland that will persist into early next week. Meanwhile, a low pressure system system is forecast to track south of the Aleutians and into the northern Gulf on Friday, with increasing prospects for precipitation across the Southern Coast, Southeast Alaska, and adjacent mountain ranges into the weekend. A deep surface low over the western/central Aleutians on Friday is expected to produce a triple point low that will likely reach the Gulf over the weekend, but may take a more southern track compared to the previous low. A third low pressure system may follow behind this for next Tuesday across the Gulf. ...Guidance Evaluation and Preferences... The latest guidance continues to have above average clustering for the first few days before returning to typical model to model differences for the later portion of the extended period. Initially there is a strong low positioned over the Gulf of Alaska and an arctic trough extending over the western portion of the mainland. Consecutive runs are confirming a stronger trough over western Alaska with more hints of an upper low trying to develop. Model differences remain this cycle with the progression of the next strong low in the general vicinity of the Aleutians. The GFS, and to some degree the the CMC, has been persistent on a faster, wetter system than the ECWMF/UKMET. There is good model support for a triple point low forming as this low approaches the Gulf on Saturday with a fast eastward track, and a rapid weakening of the parent surface low to the northwest. For early next week, the CMC/ECMWF support the idea of another surface low entering the Gulf, whereas the GFS has a weaker and much slower system. The preferred model blend began with a general consensus of the CMC/GFS/UKMET/ECWMF and then transitioned to a heavier weighting of the ECWMF/CMC and EC ensemble means for the mid and latter periods. Overall, this maintained decent continuity with the previous WPC Alaska forecast. ...Weather/Hazards Highlights... Southeast Alaska will have periods of coastal rain and mountain snow on most days as a few surface lows and frontal systems affect the region. Precipitation accumulations are generally expected to be in the 2 to 4 inch range for this part of the state. Precipitation (rain and mountain snow) should extend back into the Southeast Coast/AK Peninsula and portions of the mainland under general unsettled flow/troughing, but not as heavy. The Aleutians should stay wet and unsettled for much of the forecast period as several systems move through the region. Colder air will filter into portions of northern and western Mainland behind a cold front resulting in below average temperatures for early March into next weekend. Widespread subzero lows are expected for western and northern portions of the mainland, with perhaps some -30s across the normally colder locations of the North Slope. Campbell/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