Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 757 PM EDT Tue Sep 27 2022 Valid 12Z Sat Oct 01 2022 - 12Z Wed Oct 05 2022 ...Strong storm likely in the Bering Sea near the Aleutians late week... ...Overview... Energy from what is currently Tropical Storm Kulap in the western Pacific will lead to a strong extratropical low system over the Bering Sea late week, with strong winds and some light precipitation over the Aleutians. As the weakening but remaining low system taps into more moisture as it crosses into the Gulf, enhanced precipitation is likely from Southcentral Alaska into the Panhandle. ...Guidance/Predictability Assessment... The main concern as the period begins 12Z Saturday will be with the positioning of the surface low and energy aloft stemming from Kulap. The past couple of ECWMF runs showed a more eastern position than the bulk of other deterministic guidance, which overall seems slower than guidance/forecasts from a day ago. Ensemble means were somewhat in between but leaned a bit on the western side. Though the ECMWF seemed okay in other aspects of the forecast, the WPC forecast used a model blend without the EC that instead favored the GFS along with smaller proportions of the CMC and UKMET early in the forecast period. The deterministic ECMWF thus has the surface low crossing the Aleutians/Alaska Peninsula faster than other guidance early next week and a blend of the GFS/CMC and ensemble means still seemed like a good middle ground, with the UKMET hovering a bit west of consensus. In any case this feature should enhance persistent but weak troughing over the western mainland and the Aleutians/Alaska Peninsula through the period, with more uncertainty on whether or not troughing reaches eastern Alaska. One related factor will be the track of a shortwave/small closed low likely near the Aleutians Monday/Tuesday. The 12Z ECMWF and GFS were not too far off with this feature, while the CMC is also in line early but seems to go awry by Tue. With the deterministic models diverging considerably, more ensemble mean guidance was used for the latter part of the period, particularly the EC mean, while the operational GFS remained in the blend as it seemed to be a good proxy for ensemble positions while helping maintain some strength of systems. ...Weather/Hazards Highlights... An initial shortwave and low near the Panhandle could cause lingering precipitation there as the period begins Saturday. But bigger impacts will likely be from Kulap's energy as its surface low brings the possibility of strong winds to the Aleutians into Saturday, as well as some precipitation there. As the low pressure system progresses across the Bering into the Gulf, additional Pacific moisture should come into play and lead to modest to potentially heavy precipitation (higher elevation snow and lower elevation rain) from the Kenai Peninsula eastward into Southcentral and especially northern parts of the Panhandle, which should linger there for a few days. Light showers, possibly in the form of snow, are also possible across parts of Interior Alaska. Temperature anomalies are not forecast to be too strong, and highs will be generally above average for the interior between the Brooks and Alaska Ranges, with pockets of below average within those ranges and for the southern part of the state. Expect around normal to mainly above normal temperatures for lows. Tate Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri-Mon, Sep 30-Oct 3. - Heavy precipitation across portions of the Alaska Panhandle, Fri, Sep 30. - High winds across portions of the Aleutians, Fri-Sat, Sep 30-Oct 1. 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