Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 630 PM EDT Wed Sep 22 2021 Valid 12Z Sun Sep 26 2021 - 12Z Thu Sep 30 2021 ...Guidance and Predictability Assessment... The synoptic pattern for the extended period generally is an upper-level low that drifts southward from the Arctic Circle with spokes of upper troughing pinwheeling within the flow across the state and the Gulf of Alaska. Initially, a potent surface low will have already spread heavy precipitation across the Southeast just prior to the beginning of the extended forecast and there will be some lingering precipitation to start. Another surface low is forecast to track across the northeastern Pacific and cause another round of precipitation for the Panhandle early next week. Then, another low that could be reasonably deep for this time of year is currently expected to move from the Bering Sea southeastward across the Aleutians into the Gulf of Alaska, which could cause increasing precipitation chances for southern Alaska and the Panhandle dependent on the low track.Additionally of note, the Joint Typhoon Warning Center has begun issuing advisories for T.D. Twenty that will be strengthening while tracking over the western Pacific-- is forecast to be near 140E by the 27th. There continues to be timing and depth differences among the guidance that decreases confidence on exactly where and when the moderate to heavy precipitation will occur; however this pattern is favorable to keep much of the state cooler and the Southeast wet. WPC continued to prefer the slower solutions since they clustered well with the ensemble means. Therefore to maintain a since of continuity from the previous forecast, the blend utilized 12Z ECWMF/GFS along with the EC ensemble and the GEFS means-- with increasing weighting of the means through the middle and later periods. ...Sensible Weather... Some precipitation is expected to linger while the Southeast gets another round of precipitation early in the coming week as a strong low approaches in the Gulf. Gusty winds will accompany this low for areas offshore. Farther north, central/eastern parts of the mainland could see moisture and increased precipitation (some falling as snow) chances this weekend. A secondary low, just as potentially strong as the initial one, could bring gusty winds and precipitation to the Aleutians and toward South-central Alaska and eventually the Panhandle again by midweek. The exact track and strength of this low remains uncertain. The upper trough persisting over the mainland will keep temperatures below normal over much of the state through the extended period. Coldest anomalies should be over the southern parts of the state and across higher elevations of the Brooks and Alaska Ranges. Daily maximum temperatures are expected to range from the 40s and 50s in coastal areas, while highs could remain in the 30s or lower across much of the mainland. Campbell Hazards: - Heavy precipitation across the Alaska Panhandle, Wed, Sep 29. 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