Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 722 PM EDT Sun Oct 22 2023 Valid 12Z Thu Oct 26 2023 - 12Z Mon Oct 30 2023 ...Synoptic Overview... The main feature for the extended forecast period through Saturday will be an anomalous and large upper ridge/closed high centered near the southern mainland coast, potentially reaching 576 dm. It will likely serve as a blocking feature through the end of the week before gradually eroding, keeping most of the mainland dry. Some changes are on the distant horizon with a low pressure system originating from the Kamchatka Peninsula that'll head in the general direction of the southern Bering and the central Aleutians by late Friday, and should be strong enough to at least displace the ridge axis some to the southeast, closer to the southeast Panhandle region. This storm system would increase the prospects for precipitation across western Alaska and the Aleutians, also with some gusty winds. ...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 to end of next week, and the GFS has come more into line with the model consensus compared to its run yesterday that portrayed an outlier solution with a low crossing the Alaska Peninsula. Therefore, a nearly multi-deterministic model blend suffices as a starting point in the forecast process for Thursday and into Friday. Looking ahead to Saturday, the 00Z runs of the ECMWF and the ECENS maintained the upper high farther northwest of the current 12Z model consensus, and the new 12Z ECMWF has trended in the direction of suppressing the upper ridge a little faster and now more in line with the GFS/GEFS/CMC. By Sunday and into Monday, the CMC has a stronger low south of the Aleutians that does not have much other model support, so this is less favored by the end of the forecast period. There is a gradual increase of the ensemble means going into next weekend and into Monday, accounting for about half of the forecast blend by that time, with a little more weighting to the GEFS mean compared to the 00Z ECENS. ...Weather and Hazards Highlights... Temperatures across the state are expected to range from the mid 20s to near 40 degrees for highs across most inland areas, and lows generally from the mid 10s to near 30 degrees, locally colder in the normally colder sheltered valley locations. Temperatures will also be highly dependent on whether valley inversions can mix out during the day. Highs in the 40s and lows in the 30s are generally expected for the southern coastal areas. In terms of precipitation prospects, there has been an overall increase in expected rain and inland snow for the western third of the state compared to yesterday's forecast, since the Bering Sea low has trended more impactful for late Friday and into the weekend. The highest QPF is expected for the upslope terrain of the Alaska Peninsula and the eastern Aleutians where moisture advection from the North Pacific will be sustained the longest. Moderate to locally heavy snow is possible for portions of the western Interior, and even some instances of freezing rain will be possible. 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