Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 623 PM EST Wed Jan 19 2022 Valid 12Z Sun Jan 23 2022 - 12Z Thu Jan 27 2022 ...A wet pattern with heavy precipitation possible will continue into the first half of next week for Alaska's southern coast and Panhandle... ...Overview... Guidance continues to show a very warm and wet pattern for early next week, as a strong eastern Pacific mean ridge extends northward into Alaska's mainland and northwestern Canada while a mean trough axis persists farther west, with an embedded initially fairly deep upper low over eastern Siberia that should drift northward with time. This pattern and a shortwave and surface low affecting the Alaska Peninsula and southwest mainland Sunday-Tuesday will direct moist flow into the state and cause precipitation for western and southern parts of the state spreading eastward with time, with the highest totals likely over the southern coast and Panhandle. Weak upper troughing and cooler/drier surface high pressure is forecast to push west to east across much of the mainland around midweek onward as the ridge axis relaxes and shunts eastward into Canada. ...Guidance/Uncertainty Assessment... Model agreement at the beginning of the period is fairly good with the overall pattern described above. The upper low and associated surface low/frontal system initially located west of the state has a slightly slower trend compared to yesterday's model guidance and WPC forecasts as they track northwest while weakening, but there is good agreement for the upper ridge axis farther east across much of the mainland and Panhandle through the early part of the week. For the most part, guidance has also come into fairly good agreement with a mid-upper shortwave and a surface low track near the Alaska Peninsula around Monday, though there remain differences with the exact timing of the low and whether it will track north of the peninsula into Bristol Bay or south. The main outlier with these features was the UKMET, which was farther west than the consensus of other guidance, so the early part of the medium range forecast was based on a blend of the deterministic ECMWF/GFS/CMC. For days 6-8 (Tuesday-Thursday), troughing should weaken but press into the northwestern parts of the mainland, but other than that the details are quite nebulous regarding shortwaves and the track of surface lows especially for the western part of the state and the fairly progressive northern Pacific flow. Thus the medium range forecast blend quickly ramped up the proportion of GEFS and EC ensemble means for days 7-8 given the deterministic model differences and no perfect solution at this point. ...Weather/Hazard Highlights... The deep layer southerly flow will bring in significant moisture (precipitable water values generally +1.5 to +2.5 standard deviations above normal) into Alaska for the first half of the week. The highest precipitation totals are likely from the Alaska Peninsula into Southcentral Alaska and spreading eastward into mainly northern parts of the Alaska Panhandle, with a possible period of gusty winds. Some snow is forecast to spread into the western part of the mainland as well in conjunction with a frontal system. A drier trend is likely by Thursday as high pressure builds in. Much above normal temperatures are predicted early next week underneath the upper-level ridge, with widespread temperatures 15-30F above average (locally higher) for much of the mainland except the far western part. Temperatures will moderate closer to normal and even shift to below normal from west to east on Tuesday through Thursday as the ridge moves away from the state. Tate Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat, Jan 22. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sun-Mon, Jan 23-Jan 24. - High winds across portions of the Alaska Panhandle and mainland Alaska, Mon, Jan 24. 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