Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 644 PM EST Mon Mar 4 2024 Valid 12Z Fri Mar 8 2024 - 12Z Tue Mar 12 2024 ...General Overview... An upper level trough and accompanying cold front is forecast to extend southward from the Arctic going into the end of the work week and 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. 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 12Z model guidance suite generally featured above average synoptic scale agreement on Friday with the strong low over the Gulf and the arctic trough extending over the western portion of the mainland. There has been a trend for a stronger trough over western Alaska through the weekend with more hints of an upper low trying to develop. Farther south, there are some timing differences with the progression of the next strong low in the general vicinity of the Aleutians, with the CMC and GFS faster than the UKMET/ECMWF. There is good model support for a triple point low forming as this low approaches the Gulf on Saturday, and this is also strongly supported by the latest machine learning (ML) guidance 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 ML guidance favors something closer to the CMC/ECMWF guidance late in the forecast period. The WPC progs incorporated increasing proportions of the ensemble means into the blend through the Sunday to Tuesday time period, with a roughly 50/50 blend of the deterministic models and ensembles by Tuesday. Overall, this maintained decent continuity with the previous WPC Alaska forecast. ...Weather/Hazards Highlights... Periods of coastal rain and mountain snow are expected on most days across Southeast Alaska through the period as a few surface lows and frontal systems affect the region. Multi-day totals of 2 to 4 inches of precipitation is possible, especially next weekend across the coastal mountain ranges where orographic forcing is maximized. 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. In terms of temperatures, a cold front crossing western mainland Alaska will bring readings back down to below average levels by early March standards for the western half of the state, and the North Slope, by the end of the week and lasting into the 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. 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