Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 656 PM EST Sun Feb 20 2022 Valid 12Z Thu Feb 24 2022 - 12Z Mon Feb 28 2022 ...Heavy precipitation along the southern coast of the mainland continuing at least through Thursday-Friday... ...Overview... Today's guidance once again shows a broad region of cyclonic flow between a mean low near Kamchatka and a very amplified upper ridge settling into Canada and the Arctic. There is relative agreement that this pattern will support multiple days of precipitation, heavy at times, focused along the southern coast of the mainland. Some moisture could eventually reach the Panhandle. Many areas will also see above normal temperatures, with much above normal readings most likely over the northwestern half of the mainland. There is still considerable uncertainty regarding individual shortwaves and surface systems/fronts across the North Pacific into Gulf of Alaska and Bering Sea though. ...Guidance/Predictability Assessment... The forecast maintained a blend approach to emphasize the most similar aspects of the large scale pattern and some embedded features while downplaying less confident aspects. As in recent days, the 12Z operational models provided the starting point for the first half of the period while 12Z GEFS/00Z ECens weight quickly increased to 40-50 percent total by days 7-8 Sunday-Monday. During the first half of the period the primary focus will be on low-predictability shortwave details that will affect one or more surface waves expected to track over an area encompassing the North Pacific through Alaska Peninsula and Bering Sea. The best signal at the moment is for one wave to track over this area Thursday into Friday and then for a second wave that may track somewhat farther east (perhaps near Kodiak Island) as shortwave energy may elongate a little eastward by Friday-Saturday. ECMWF/ECMWF mean runs have been weaker and faster with the latter feature than most other models/means, but at least share the more general idea of a front with a leading band of enhanced winds advancing across the Gulf of Alaska. By later in the weekend and early next week the surface pattern should relax somewhat along the southern coast while a system develops upstream over the Pacific, with the supporting upper trough forecast to reach near 150W longitude by next Monday. Over the past day the best clustering of guidance has gravitated somewhat southward with this system which is toward yesterday's GFS. There is a moderate amount of north-south spread for this system which is expected to be south of Kodiak Island by next Monday. Also at that time guidance is showing a strengthening system that may begin to influence the western Aleutians early next week. Ensemble means are very similar while operational models show typical spread for specifics. ...Weather/Hazard Highlights... Guidance is maintaining the general signal for a period of locally heavy precipitation along the southern coast during the latter half of the week, focused by an area of brisk to strong winds across the Northeast Pacific/Gulf of Alaska. Important surface wave/front details will take additional time to resolve due their relative small scale leading to low predictability. Today there appears to be somewhat better potential for meaningful precipitation to extend into the southeastern coast and Panhandle by late week and the weekend, with some moderate to heavy activity possible. Highest totals for the overall period should be near the Kenai Peninsula. Some moisture may extend farther north over the mainland but with much lower totals. Precipitation should trend lighter by Sunday-Monday. A strengthening system may bring increasing winds/precipitation to the western Aleutians by next Monday. The forecast continues to show above to much above normal temperatures over most of the state through the period. The greatest anomalies of plus 20-30F, and over some areas even warmer, are most likely over the northwestern half of the mainland. The primary exception to this warmth will be moderately below normal highs over the southern two-thirds of the Panhandle. In general expect the anomalies for min temperatures to be somewhat warmer relative to those for the highs. Rausch 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