Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 759 PM EDT Wed Oct 20 2021 Valid 12Z Sun Oct 24 2021 - 12Z Thu Oct 28 2021 ...Overview and Guidance/Predictability Assessment... Today's main issue in the medium-range period continues to be the large spread in the model guidance regarding the next cyclone forecast to track close to the Aleutians next Sunday into Monday. The latest (i.e. 12Z) ECMWF now takes a stronger cyclone closer toward the western/central Aleutians on Sunday in better agreement with the GFS. But then these two models diverge markedly, with the ECMWF ejecting the low well to the east while the 12Z GFS keeps the low well to the west, not far away from the Aleutians. The 06Z GFS did not keep the cyclone as far west as the 12Z run. On the other hand, the ensemble means are generally right in the middle of these two model extremes. This calls for adopting toward an even blend of the ensemble means by next Monday, which yielded a solution fairly close to continuity from yesterday. Beyond this time frame, the ensemble means generally agree with keeping a broad cyclonic circulation to meander in the vicinity of the Gulf of Alaska. Therefore, the WPC forecast grids for Alaska were based on a blend of the 06Z GFS/12Z GEFS, the 12Z ECMWF/12Z EC mean, together with smaller contributions from the 12Z CMC/CMC mean. The blend quickly was skewed toward the ensemble means by Day 5 (Monday). ...Weather/Hazard Highlights... The medium range period will likely begin with subsiding winds over the eastern Aleutians and the Alaska Peninsula early next Sunday as a deep cyclone gets absorbed into a broad cyclonic circulation over the northeastern Pacific. Meanwhile, models came into better agreement for the next potentially deep cyclone to track just south of the Aleutians around Sunday, possibly bringing a brief period of enhanced rainfall together with a risk of high winds. Effects on the Aleutians will be very sensitive to the exact strength/track/timing of the storm. The best chance for high winds should come late Sunday into Monday from the back-side of the cyclone as it tracks away to the east. Thereafter, flow around a potential Bering Sea wave may increase precipitation somewhat over areas between the eastern Aleutians and southwestern mainland Tuesday-Wednesday. Shortwaves on the east side of the large scale mean trough aloft may produce occasional episodes of precipitation over parts of the mainland. The southern coast/Panhandle could see a modest increase of rain/snow toward midweek as a broad cyclone is indicated by the models to meander over or south of the Gulf of Alaska. Expect above to much above normal temperatures over the northern two-thirds or so of the mainland through the weekend and into early next week followed by some moderation as heights aloft slowly decline. The southern mainland and Alaska Peninsula plus the Panhandle will likely see a mix of above/below normal readings (more above for min temperatures) with a trend toward greater coverage of below normal anomalies by midweek. Kong/Rausch 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 Hazards: - No significant hazards are expected over Alaska during this forecast period. 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