Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 532 PM EST Sat Mar 9 2024 Valid 12Z Wed Mar 13 2024 - 12Z Sun Mar 17 2024 ...General Overview... An amplified upper level flow pattern is expected to be in place across the Alaska domain for the second half of the week and extending into next weekend. A persistent upper trough over the western half of the mainland will equate to below average temperatures for much of the forecast period. Meanwhile, an elongated upper ridge axis with potential closed higher over eastern Siberia, and a building ridge axis over western Canada, will tend to result in a rather blocky pattern that keeps the western Alaska upper trough in place. A few surface lows will track eastward towards the Gulf region and produce rounds of unsettled weather from the Alaska Peninsula to the southeast Panhandle. ...Guidance Evaluation and Preferences... The 12Z model guidance suite is in better overall synoptic scale agreement for the Day 4 period compared to yesterday, which featured greater differences between the GFS and non-NCEP guidance. Going in Thursday, the UKMET becomes stronger with the low tracking northeast over the Gulf compared to the model consensus, and then well south of the consensus with a trailing surface low. Looking ahead to next weekend, the GFS is northwest of the model consensus with the track of the triple point surface low tracking south of the Aleutians, whereas the CMC/ECMWF take that low much farther south. By next Sunday, there is quite a bit of model spread with upstream shortwaves near the western Aleutians, but continued decent agreement across northern mainland Alaska. Given increasing uncertainty in subsequent surface low evolutions across the North Pacific, the ensemble means accounted for about half of the forecast blend by next weekend. ...Weather/Hazards Highlights... Multiple rounds of moderate to heavy rain and mountain snow are expected from the eastern mountains of the Alaska Peninsula to the southeast Panhandle during the extended forecast period. A potential atmospheric event on Wednesday for the Panhandle could bring a few inches of liquid equivalent precipitation by Thursday morning. The period with the best potential for moderate/heavy rain and snow will be Friday afternoon into Saturday from the Kenai Peninsula to the St. Elias Mountains. There may also be some strong gap winds for the usual coastal locations at times. Temperatures for a vast portion of western and especially northern Alaska will be quite cold for the middle to end of the week, and thus well below average for early/mid March. Widespread subzero lows are expected for western and northern portions of the mainland, with widespread -20s across the North Slope for the middle to end of the week. There will likely be a gradual moderating trend going into next weekend. 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