Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 748 PM EDT Sat Oct 28 2023 Valid 12Z Wed Nov 01 2023 - 12Z Sun Nov 05 2023 ...Overview... The persistent upper ridge over much of the state looks to last through around Thursday or Friday of next week, when energy tracking westward should erode the ridge and replace it with troughing over the Interior. This will cause much above normal temperatures to reduce in magnitude and scope by late week, as a cold front tracks southward through the state. Farther west, an upper low over the Bering Sea at the start of the period Wednesday will track southeast into the northern Pacific and join another upper low there. Low pressure both at the surface and aloft should linger through next weekend. This pattern will favor some periods of precipitation across the Alaska Peninsula to Southcentral and Southeast Alaska, but nothing terribly heavy is expected. ...Guidance Evaluation and Preferences... Model guidance is in reasonable agreement during much of the medium range period, with typical differences in the details. There are some slight timing/placement discrepancies with the upper low crossing the Aleutians on Wednesday-Thursday, with the GFS runs slower than other guidance with taking the feature southeast, especially the 06Z GFS run. This also leads to the feature initially in the northern Pacific tracking east maintaining a shortwave in the GFS for longer, while other guidance has the initial feature absorbed a bit more quickly. Then with the pattern changing from ridging to troughing across the Interior, there are some timing and magnitude differences with the energy serving to create the troughing. The energy could perhaps be from two sources, dropping south from the Arctic and tracking west from a north-central Canada low. Some model runs like the 12Z GFS and the 00Z ECMWF especially have been more aggressive in bringing in stronger energy faster (though the 12Z ECMWF backed off on this). A middle ground on timing and strength seems best. Overall the guidance seemed well within typical spread for the time frame. Thus the WPC forecast used a blend of the deterministic models (12Z ECMWF/GFS/CMC/UKMET) for the early part of the period, and gradually increased the proportion of the GEFS and EC ensemble means with time, but to half the blend only by Day 8 given the reasonable model agreement on the large scale. ...Weather and Hazards Highlights... Precipitation across the state should be generally light to moderate through the period, and timing of the precipitation will depend on the details of upper and surface low positions particularly in the northern Pacific. The pattern should cause most precipitation to be limited to the southern coast. Areas from the Aleutians and the Alaska Peninsula into Kodiak Island and the Kenai Peninsula/Southcentral Alaska are likely to see precipitation a bit enhanced through Wednesday-Thursday, with some chances of light precipitation lasting into late week as well. Southeast Alaska will see precipitation chances increasing by Thursday-Friday with some light to moderate amounts expected. Farther north, there could be a bout of light snow across the northern tier through Wednesday, and some snow could sneak north into the Interior by the weekend. Where precipitation occurs, the precipitation type will favor coastal/lower elevation rain and interior/higher elevation snow. The milder than average temperatures in the short range are likely to continue into Wednesday and Thursday, but gradually moderating in magnitude from 20F+ anomalies on Wednesday to more like 10F+ anomalies on Thursday in the northern tier and the southwestern Mainland. As the upper ridge erodes and a cold front pushes through, temperatures will moderate closer to normal, perhaps even slightly below normal for highs by late week in parts of the Interior. The North Slope is likely to stay above average though with some milder onshore flow. Meanwhile Southeast Alaska and the Aleutians look to see temperatures generally within a few degrees of average. Tate 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