Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 756 PM EDT Sat Oct 21 2023 Valid 12Z Wed Oct 25 2023 - 12Z Sun Oct 29 2023 ...Synoptic Overview... The main feature for the extended forecast period mid to late week will be a large upper ridge/closed high centered near the southern mainland coast that will likely have some staying power. It will likely serve as a blocking feature through at least Friday and possibly into Saturday before gradually eroding, keeping most of the mainland dry. Some relatively weak storm systems are likely to cross the Aleutians and into the Bering, but these should mainly provide light precipitation and some gusty winds over the open waters. ...Guidance Evaluation and Preferences... The 12Z model guidance suite has a good overall depiction of the synoptic scale pattern across the Alaska domain for the middle of next week, although one of the main differences involves the GFS with a surface low tracking north across the eastern Aleutians that is not reflected in the other guidance, although it is similar in most aspects across the mainland. The forecast blend was primarily weighted towards the UKMET/CMC/ECMWF through Thursday, and then a gradual increase of the ensemble means going into next weekend, accounting for 50-60% of the forecast blend by that time. ...Weather and Hazards Highlights... Temperatures across the state are expected to range from the low 20s to upper 30s for highs across most inland areas, and lows generally in the 10s and low 20s, except for some 0s in the normally colder sheltered valley locations. Temperatures will also be highly dependent on whether valley inversions can mix out during the day, but if they don't, temperatures may actually be colder than average for the lowest elevations of the Interior, while the surrounding hills may be considerably warmer owing to the ridge in place. Highs in the 40s and lows in the 30s are generally expected for the southern coastal areas. The best prospects for rain will be from the Alaska Peninsula to the central Aleutians, and mainly dry conditions elsewhere. Hamrick 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