Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 702 PM EST Wed Mar 09 2022 Valid 12Z Mon Mar 14 2022 - 12Z Fri Mar 18 2022 ...Overview... A strong shortwave is expected to round the top of the Siberia upper ridge this weekend and then dive south into the Mainland early in the week. This will allow a northeast-southwest oriented upper trough to make its way through the eastern part of the state; possibly with an embedded upper low reaching the southern coast/southwestern Mainland by the middle of the week. Farther south and within fairly active Pacific flow, a strong mid-latitude system should weaken somewhat as it approaches the Panhandle early next week. At the same time a trailing system will likely track just south of the Aleutians, but with some uncertainty over what interaction may occur between it and initial low pressure/upper dynamics lingering over the Aleutians. Some details of these Pacific systems will depend on exactly how the upper trough over the mainland evolves. ...Guidance/Predictability Assessment... The latest runs of the models and their respective ensemble means have continued to favor a deeper trend for the trough that will move through the Mainland. It was noted yesterday that a majority of the consensus pulled the upper lower further to the southwest, leading to the precipitation extending further west across the southern coast. The 12Z run of the GFS has shifted west of the 06Z solution and the 12Z ECWMF has also trended a little further west as well. The 12Z UKMET is fairly clustered with the main features but is not as deep; whereas the 12Z CMC is deeper, but is tracking faster/further east than the cluster. The deterministic and the ensemble means are all showing an upper low around the far southwest corner of the mainland. There is still some uncertainty with the track and evolution of the systems coming from the Pacific, especially for the leading low that will approach the Southeast. Regarding Pacific systems, there are still important track/evolution differences for the leading low tracking toward the Panhandle early next week. The past couple ECMWF runs have been on the southern side of the spread at that time but the 12Z run did at least trend north of its previous run. Remaining models and means show a somewhat farther north track and/or northward elongation or redevelopment in response to the amplifying mainland upper trough. Meanwhile guidance has been inconsistent with some details of the system tracking south of the Aleutians, partially due to uncertainty over how much interaction may occur with residual dynamics/low pressure over or near the Aleutians. The 12Z ECMWF is somewhat on the northern side of the spread. By late in the period the ensemble means agree that the primary focus for low pressure should eventually gravitate to the northeastern Pacific/Gulf of Alaska due to the mainland upper trough. The WPC forecast utilized a multi-model approach in order to encompass the best placement and amplitude within the cluster of solutions, beginning with the 06Z/12Z GFS/12Z ECWMF/12Z CMC/12Z UKMET (lesser weighting of the CMC and UKMET due to more variability with amplitude and placement) and transitioning to 30 percent of the ensemble means by the end of the forecast period. The inclusion of the deeper means helped reduce the noise in the Pacific while trending toward the trough/low near southwest Alaska. ...Weather/Hazard Highlights... A vast majority of the Mainland will be generally dry over the course of this forecast period while the precipitation will focus over the southern coastal areas and across the Southeast. Initially the precipitation will be light and at time moderately heavy but as the weekend progresses, the intensity and areal coverage will lessen. As the low approached the Panhandle by Monday, precipitation will increase again and expand back along the southern coast and the adjacent areas inland. Another system reaching the Northeast Pacific/Gulf of Alaska may enhance precipitation around Wednesday. Since this time period has more uncertainty, confidence on the amount coverage and intensity of the precipitation is about fair/average at this point. The Aleutians may see periods of mostly light precipitation. There will likely be brisk to strong northerly winds spreading across the Bering Sea and Aleutians by Tuesday-Wednesday. Above normal temperatures will persist this weekend over the southern Mainland and North Slope while below normal readings (especially for highs) in-between and over the eastern mainland. Temperatures will likely trend cooler as the trough settles into the mainland by early next week, changing to below normal for mid-March. Some pockets of above normal readings could linger over the North Slope and for min temperatures in the far south. Expect most of the Panhandle to see below normal highs through the period and a mix of above or below normal lows. Campbell No significant hazards are expected over Alaska during this forecast period. 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