Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 636 PM EST Wed Feb 14 2024 Valid 12Z Sun Feb 18 2024 - 12Z Thu Feb 22 2024 ...Overview... Guidance shows a deep storm near the western Aleutians this weekend drifting into the central Bering Sea and weakening by next week, while shortwave energy flowing around the southern/eastern side of the associated upper low keeps the north Pacific/Gulf of Alaska storm track active and conditions unsettled and wet from generally across the Alaska Peninsula and Southern Coast region. These systems should weaken as they reach the coast given upper ridging over the Mainland through much of the period. The biggest heavy rain threat should be towards the end of the period associated with a deep cyclone that lifts into the Gulf next Wednesday-Thursday. Another vigorous storm system looks to track across the Aleutians around next Tuesday-Thursday. ...Guidance Evaluation and Preferences... In general, the latest guidance shows good agreement on the overall evolution of the pattern and the large scale flow, but a lot of uncertainty still on the details especially individual shortwaves rounding the base of the initial mean trough in the Bering. Biggest questions surround the track of these shortwaves/storms towards southern Alaska and how much they're able to erode the ridge over the Mainland. Both the GFS and ECMWF suggest systems may be able to erode the ridge and lift northward, while the CMC shows much stronger ridging than consensus and thus suppressing the storm track well to the south mid-late period. This also affects eventual eastward movement of the next deep system towards the Aleutians late period. There is better consensus with the 12z GFS, ECMWF, and ensemble means for a reorientation of the mainland ridge to a more southeast to northwest direction (vs the CMC which has a strong north-south orientation), allowing the deep surface to track more into the central/eastern Aleutians or Bering Sea. The WPC forecast blend for today used a general model compromise with the deterministic solutions for about the first half of the period. This helped to smooth out smaller scale details differences but keep the large scale system definition/depth. By the back half of the period, incorporated the ensemble means in place of the CMC, eventually ending up with a 50/50 blend of the ensemble means with the deterministic GFS/ECMWF. Overall, this maintained generally good continuity with the previous WPC forecast. ...Weather/Hazards Highlights... The deep surface low near the west-central Aleutians to start the period will keep precipitation and gusty to strong winds across the Aleutians. Precipitation is likely to continue through much of the period as general troughing is maintained over this region, with increasing precipitation and wind chances again by the middle of next week as the next deep low moves in. Farther east, much of the Peninsula to Southern Coast/Yakatat region should be generally unsettled given an active north Pacific/Gulf of Mexico storm track with above normal precipitation across Southwest Alaska too as shortwave skirt that region. A deeper surface low lifting towards the Southern Coast may bring another round of heavy precipitation next Monday-Wednesday with multi-day precip totals of several inches possible particularly the southern Alaska Peninsula, Kodiak Island, and eastward to the Southern Coast. Much of Mainland Alaska should be mostly dry the entire period associated with upper ridging. Initial upper ridging, and then continued Pacific influence even with some erosion of the ridge, will favor above normal temperatures across most of the state. Expect the greatest anomalies to be in the western to northern parts of the mainland and possibly reaching at least 30 degrees milder than normal into the weekend. Some cooling will be possible next week but still with above normal anomalies. Some pockets of near to slightly below normal temperatures will be possible over the eastern Interior and mostly for daytime highs over portions of the Panhandle/Aleutians. 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