Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 716 PM EDT Sat Apr 06 2024 Valid 12Z Wed Apr 10 2024 - 12Z Sun Apr 14 2024 ...Synoptic Overview... A surface low is forecast to be in place over the northern Gulf as the period begins Wednesday, and drift slowly south/southeast and weaken as the parent shortwave moves inland next Friday. A period of upper ridging should briefly build over the Mainland behind this low later next week, but will shift east as the next system enters the Bering Sea and approaches western Alaska next weekend. These two systems should keep the Aleutians to Southern Coast/Southeast unsettled with rain and mountain snows. Rainfall may increase across Western Alaska as well later in the week. ...Guidance Evaluation and Preferences... The 12z model guidance today shows a good overall depiction of the synoptic scale pattern through about the first half of the period, with the exception of the UKMET which wasn't as in line with the rest of the guidance with both the Gulf low and the incoming Bering Sea low. Was able to use an equal blend of the GFS, ECMWF, and CMC for days 4-6 (Wednesday-Friday). By Friday and especially next weekend, uncertainty increases with the evolution of the Bering Sea low and an additional shortwave moving in towards the western Aleutians. The GFS suggests more interaction with the shortwave resulting in a totally phased and amplified trough across the eastern Bering/Aleutians/AK Peninsula by next Sunday as additional energy moves into the Gulf. Meanwhile, the ECMWF and CMC show a slower progression of the shortwave and less phased troughing, allowing the Bering Sea low to move closer to the West Coast of the Mainland next weekend as the shortwave slides south of the Aleutians, and ridging holds over the Gulf. Given the uncertainty, the ensemble means are fairly washed out with the details of these systems, but aren't as aggressive as the 12z GFS seems to be right now. The WPC blend for today used the ECMWF/CMC in conjunction with the ensemble means for the latter half of the period, with a 70/30 ensemble mean/operational blend by Day 8/Sunday. ...Weather/Hazards Highlights... Moderate precipitation over Southeast Alaska to start on Wednesday should slide through the Panhandle on Thursday as the initial Gulf storm weakens and the surface front moves inland. Rain and mountain snow should continue into next weekend from the Aleutians through the Southern Coast/Southeast as weak southerly flow increases moisture across these regions ahead of the upper low moving into the Bering and another weak surface front moves through the Gulf. While amounts are not forecast to be all that heavy/hazardous on any particular day, precipitation totals may add up to several inches, especially from the Kenai Peninsula to the Panhandle. Precipitation across Western Alaska may also increase Thursday into the weekend, with some enhancement across the higher elevations. Temperatures may begin Wednesday moderately cool across the southern half of Alaska, but should moderate into the weekend across most areas. Temperatures across the northern half of Alaska should see a warming trend through the period, with the Greatest anomalies, on the order of 10-20 degrees above normal, likely across the North Slope and northwest Alaska regions. Santorelli 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