Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 652 PM EST Tue Jan 18 2022 Valid 12Z Sat Jan 22 2022 - 12Z Wed Jan 26 2022 ...Heavy precipitation along the southern coast and Panhandle into the weekend, with a wet pattern continuing into next week... ...Overview... Guidance continues to show a very warm and wet pattern as a strong eastern Pacific mean ridge extends northward into Mainland Alaska and northwestern Canada while a mean trough axis persists farther west, with an initially fairly deep upper low in the northern Bering Sea that should drift northeastward with time. This pattern will direct moist flow into the state, causing significant precipitation across western and southern parts of the state, with highest totals likely over the southern coast and Panhandle. Forecast details become more uncertain after the initial system departs and the overall upper trough gradually weakens, but there is a general theme that additional significant precipitation will be possible over some areas between the Alaska Peninsula and Panhandle through next Wednesday. ...Guidance/Uncertainty Assessment... Initial model agreement is fairly good with the overall pattern described above. Recent guidance shows the embedded upper low located over the northern Bering Sea early Saturday, with surface low pressure approximately collocated. There is some uncertainty in the upper low evolution after that, with a general trend to track eastward more quickly and possibly pushing a cold front through northern/central parts of the mainland faster than the previous forecast. But within this trend, GFS runs and the ECMWF had a faster northeast track than the CMC and the ensemble means, and favored the latter cluster for this forecast to not stray from the ensemble means and be closer to continuity. Farther south, guidance generally shows a couple of surface lows initially tracking through the Pacific well south of the Aleutians northeastward likely across the Alaska Peninsula, with the current forecast into Bristol Bay early Monday per the EC mean and GFS and ECMWF, though with some uncertainty in the track. For days 6-8 (Monday-Wednesday), 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/northern Pacific. Thus the medium range forecast blend was based on a deterministic blend initially but quickly ramped up the proportion of GEFS and EC ensemble means for days 6-8 given the deterministic model differences and no perfect solution at this point. ...Weather/Hazard Highlights... A strong surge of moisture/atmospheric river (+2 to +3 standard deviations above normal) will take aim at the state Friday into Saturday given the strong flow ahead of a low pressure/frontal system tracking on the western side of the state. The highest precipitation totals are likely from Southcentral Alaska into the Panhandle on Saturday, along with some gusty winds. Some snow is forecast to spread into the western part of the mainland as well. After Saturday, precipitation should increase for the Alaska Peninsula into the southern coast in conjunction with the next frontal system, spreading eastward for the early part of the workweek along with an additional period of possible gusty winds. There remains uncertainty with exact timing, placement, and amounts though. Much above normal temperatures are predicted for the weekend into 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 could moderate closer to normal by next Wednesday, though still above average in the eastern half of the state. Tate Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri-Sat, Jan 21-Jan 22 and Mon, Jan 24. - 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, Fri, Jan 21 and 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