Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 644 PM EST Sat Feb 19 2022 Valid 12Z Wed Feb 23 2022 - 12Z Sun Feb 27 2022 ...Heavy precipitation likely along the southern coast of the mainland next week... ...Overview... Most guidance continues to show similar ideas for the large scale pattern evolution from midweek through next weekend. Consensus shows an amplified upper ridge, from the eastern Pacific through the mainland and building into the Arctic as of midweek, drifting eastward into western Canada while a mean upper low likely travels from the northwestern Pacific into the western Bering Sea and possibly retrogrades to west of Kamchatka by next weekend. A broad region of cyclonic flow between these dominant features should contain multiple shortwaves/possible upper lows with corresponding surface lows and frontal systems. Within this pattern, a band of enhanced winds migrating across the northeastern Pacific should focus significant precipitation from the Alaska Peninsula through the Kenai Peninsula/Prince William Sound region mid-late week. Some precipitation may continue along the southern coast through next weekend but with greater uncertainty for the details. ...Guidance/Predictability Assessment... The latest array of guidance again recommended an approach of emphasizing the 12Z operational models for the first half of the period (Wednesday into early Friday) followed by incorporation of 12Z GEFS/00Z ECMWF means whose total weight reached 40-50 percent by the weekend. During the mid-late week time frame, models continue to suggest a series of waves tracking from the North Pacific into the eastern/northern Bering Sea, possibly brushing the southwestern mainland if the track is on the eastern side of the envelope. These waves and supporting dynamics are very small in scale and thus have low predictability, but will be important in refining the specifics of wind/precipitation focus into the Alaska Peninsula and locations farther to the east. By next weekend the guidance displays some additional divergence for the shape of Bering Sea into northeastern Pacific cyclonic flow and the upper ridge to the east, with continued potential for one or more surface lows over the North Pacific/Gulf of Alaska and vicinity. The favored blend ultimately reflected what has been good consensus for a front reaching the eastern Aleutians early Wednesday, leading into a combination of fronts/waves Thursday and some signal for low pressure just south of the Alaska Peninsula by early Friday. This wave may track northwestward thereafter, followed by another system that could approach the Alaska Peninsula around next Sunday. The latter has some relative support from the latest ensemble means but confidence is too low at this time to depict as strongly as in the past couple ECMWF runs and farther south GFS. ...Weather/Hazard Highlights... A band of brisk to strong winds will migrate eastward across the North Pacific/Gulf of Alaska and eastern Bering Sea/western mainland mid-late week, ahead of an initial front early Wednesday with additional waves and fronts thereafter. The flow of Pacific moisture will focus significant precipitation over the Alaska Peninsula and extending eastward at least through the Kenai Peninsula. Some of the moisture could spread farther north into the southwestern mainland with lesser totals. Confidence remains fairly low regarding the specifics of individual surface waves that would have an important influence on precipitation/wind details. From about Friday into the weekend there is also decreasing confidence in larger-scale aspects of precipitation. These include how much moisture continues eastward into the southeastern coast and Panhandle, and whether another system could begin to increase activity once again over the eastern Aleutians/Alaska Peninsula by next Sunday. Above to much above normal temperatures will prevail over most of the state through the period, with best potential for plus 20F and greater anomalies over northern and western portions of the mainland. The primary exception to the warm theme will be the southern two-thirds of the Panhandle which will likely see below normal highs on most days. 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