Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 653 PM EST Fri Jan 20 2023 Valid 12Z Tue Jan 24 2023 - 12Z Sat Jan 28 2023 ...Prolonged threat of heavy precipitation expected along the southern coast to the Panhandle for much of next week... ...Overview... With an overall trough-ridge pattern across Alaska Tuesday-Thursday, rounds of heavy precipitation remain a threat across southeastern coastal parts of the mainland as well as the Panhandle. Then ridging building in should lessen precipitation chances for the Panhandle and help create above normal temperatures for the bulk of the state, while the Aleutians to perhaps the western mainland and the Alaska Peninsula may see more active weather. ...Model Guidance/Predictability Assessment... Model guidance has stayed reasonably well clustered for the overall pattern evolution but with typical differences in the details. One trend in recent guidance was a better chance for a closed upper low to form across the north-central mainland Tuesday diving southwestward Wednesday atop the Seward Peninsula. EC runs have been persistent with this and the CMC joined this camp, with the UKMET and GFS showing hints of it as well. The track of this closed low or at least trough axis does affect positioning of precipitation across the mainland. Guidance is reasonably agreeable with a notable shortwave tracking eastward Tuesday-Thursday across the Aleutians to Alaska Peninsula to Southcentral Alaska, and ridging building into the mainland after that. Meanwhile, a deep and large surface low pressure system looks to develop in the far western Bering Sea in and around the Kamchatka Peninsula. Models show central pressures in the 930-940mb range at times. While there are some variations with its track, at least at this point models do not show this low tracking toward Alaska but show it weakening farther west instead. It does create some differences with potential for shortwave energy and surface lows across the Aleutians eastward as frontal boundaries associated with the system pass through. The WPC forecast was based on a blend of the ECMWF/GFS/CMC deterministic models early on with incorporation and increase of the ensemble means by days 6-8 given the increasing uncertainty/detail differences. ...Sensible Weather and Potential Hazards... A trough pattern across the northern to northwestern Alaska Mainland, as well as shortwaves and lows tracking across the Aleutians to the Alaska Peninsula and Southcentral Alaska, will direct moisture into the Panhandle for additional rounds of heavy rainfall through around Thursday. Ridging set up there will cause temperatures to be milder than average for a precipitation type of predominantly rain for much of the Panhandle region. Meanwhile, cooler than normal temperatures are generally expected north of the Alaska Range through Thursday in association with the upper trough/low. The Brooks Range to the North Slope can likely expect subzero high temperatures. Some residual moisture from the southern coast should make it northward into interior Alaska and precipitate as light snow through much of next week. By late next week, ridging becoming established into the mainland as well should help moderate temperatures to above normal across the state with the exception of the near-normal Aleutians. Additionally, this should begin a drying trend across the Panhandle. A large surface low pressure system is forecast over the western Bering Sea/Kamchatka Peninsula for the latter half of the week. While guidance currently has this low slowly weakening well west of Alaska, there is the potential for its frontal boundaries to come across the Aleutians and toward the southwestern mainland/Alaska Peninsula around Thursday-Saturday, along with shortwave energy. Enhanced precipitation and perhaps some high winds are possible, but the details remain quite nebulous at this time. Tate Hazards: - Heavy precipitation across portions of the Alaska Panhandle and the southern coastal sections of Alaska, Mon-Thu, Jan 23-Jan 26. 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