Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 317 PM EDT Sun Oct 20 2019 Valid 12Z Thu Oct 24 2019 - 12Z Mon Oct 28 2019 The deep storm forecast to be near the Alaska Peninsula late in the short range period (midweek) will weaken and progress eastward later in the week, leading to a gradual lighter trend for initially enhanced precipitation along the southern coast/Panhandle. Meanwhile the very deep extratropical reflection of Typhoon Neoguri will likely track near the Aleutians late week and begin a pattern evolution toward greater amplitude and slower progression. From Sat onward the details become hazy on specifics of the parent surface low, a possible frontal wave farther north over the eastern Bering Sea, and one or more waves that may track northward along/ahead of the Pacific front associated with the parent low. Regardless of the finer details there is a decent signal for a strong and persistent flow of significant moisture/precipitation aimed at the Alaska Peninsula and parts of the southern coast of the mainland by the end of the week/next weekend. Some of this moisture will overspread other portions of the mainland. Extratropical Neoguri will produce areas of strong winds and high waves as well. Guidance clustering has improved significantly for the system expected to weaken over the southwest corner of the mainland by Thu. An operational model blend reasonably represents consensus while accounting for lingering detail uncertainties, with timing a little slower than the latest ensemble means. This seems reasonable as recent trends have shown solutions gravitating toward the middle to slower half of the prior guidance spread. For the most part the models and ensembles cluster fairly well for extratropical Neoguri near the Aleutians into day 5 Fri. After that time solutions diverge (more north-south than east-west) for the parent low. There are also indications of a possible frontal wave to the north over the eastern Bering Sea, plus various ways of depicting one or more waves that may lift northward along/ahead of the front associated with the initial parent low. Trending the operational model blend early in the period to an even model (00-06Z GFS and 00Z ECMWF/CMC) and ensemble mean (06Z GEFS/00Z ECMWF mean) blend provides a good balance of reflecting the most agreeable aspects of the large scale pattern and providing a hint of individual wave details. Toward the end of the period day 8 Mon the guidance is very widely dispersed regarding the extratropical evolution and track of current Typhoon Bualoi. In addition models and even ensemble means have been inconsistent for timing. The model/mean blend preferred above provides an appropriately conservative forecast, minimizing effects on the Aleutians until confidence can improve. Across higher latitudes the main trend over the past day is toward more troughing near the northwest corner of the mainland during the first half of the period. The initial blend provides a good account for this trend while not committing to a specific scenario--given the fairly new nature of this trend and current guidance spread. Also of note, by day 8 Mon the overwhelming majority of models and ensemble means would suggest the 12Z GFS becomes too quick with its eastward progression of eastern Bering upper low/trough energy. Rausch Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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