Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 643 PM EDT Thu Jun 15 2023 Valid 12Z Mon Jun 19 2023 - 12Z Fri Jun 23 2023 ...Overview... The period starts Monday with an upper low near the central-eastern Aleutians, another one near northeast Russia/the Arctic, and a somewhat blocky ridge over Mainland Alaska. The southern low looks to progress east near/over the Peninsula before it gets forced southward into the northeast Pacific by the eastern Gulf/Alaska ridge later next week. Meanwhile, the northern low should sort of meander or maybe rotate westward sending some lowering heights across the North Slope region. Another deep low to the West should approach the region, with the better consensus saying it crosses the west-central Aleutians around Thursday and into the Bering Sea on Friday. The upper ridge in the Gulf of Alaska and the Southcentral looks to hold strong through next week. ...Guidance Evaluation/Preferences... The overall large-scale/synoptic pattern across Alaska shows some agreement through next week, including a continuing somewhat blocky upper ridge over the Gulf and at times into Alaska. There remains plenty of disagreement in the timing, strength, and details of individual systems though, even as early as day 5 (Tuesday). With the initial low near the Aleutians, the 12z GFS was a distinct outlier wanting to lift this system north into the Bering Sea, whereas the rest of the guidance (with ensemble support) prefers to move the low east and then south, as it undercuts the ridge in the Gulf. The low to the north shows somewhat better agreement with the latest 12z runs today, but the ECMWF is slightly more aggressive with the height falls into the northern Mainland (though not as aggressive as it's 00z run). The next system approaching the west-central Aleutians (around mid week) shows some problems early on regarding individual pieces of energy rotating around the main parent upper low, and multiple low pressure centers at the surface. There's low predictability in these, and so it seems the best approach is to lean towards the ensemble means for placement. The CMC was an outlier late week in keeping this system south of the Aleutians, versus the GFS/ECMWF and ensemble means favor the system crossing the Aleutians and moving into the Bering Sea. The WPC blend for today favored the 12z ECMWF and smaller contributions from the deterministic models days 4 and 5. By day 6, removed the GFS due to issues with the upper low south of the Peninsula. The late period blend was heavily weighted towards the ensemble means, but with some minor amount of the 12z ECMWF for added system definition and depth. Overall, this approach fits well with yesterdays WPC continuity. ...Sensible Weather and Potential Hazards... Showers should increase over the central-eastern Aleutians and progress towards the east-northeast in advance of the first system, but overall amounts still look to be light to modest at best. Showers may increase across the Southcentral as well, but mostly dependent on how close the low comes to the coast. Over the North Slope and the Interior, showers will be more widespread, possibly locally heavy at times. Temperatures will be mostly below normal for much of the Mainland, but could be warmer than normal for some areas of the Eastern Interior. Southeast Alaska should be warm and dry through next week with influence from the blocky upper ridge. Santorelli No significant hazards are expected over Alaska during this forecast period. 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