Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 454 PM EDT Thu Aug 11 2022 Valid 12Z Mon Aug 15 2022 - 12Z Fri Aug 19 2022 ...Cool/wet-to-snowy pattern for the North while rounds of heavy rainfall likely across the South & Panhandle... ...Guidance/Predictability Assessment... The guidance has apparently completed its slowing and strengthening trend with the western AK upper trough/upper low, which now shows a touch of retrogression before a modest return early to late next week. The guidance is beginning to cluster better concerning the northeast Pacific low/first cyclone this period moving into AK from the south Tuesday night into Wednesday. Since agreement was reasonable early on, used a compromise of the 12z GFS, 12z Canadian, 12z UKMET, and 12z ECMWF for the pressures/500 hPa heights/winds early next week. Starting late Tuesday, there is disagreement concerning the low incoming from the west and southwest (Post-Tropical Cyclone 09W). The 12z NAEFS mean and 00z ECMWF offered a more consolidated surface low like the 12z GFS, which led to its inclusion in the mix. The idea of a triple point low emerging from the Bering Sea/Aleutians into the northeast Pacific Wednesday into Thursday is being latched on to by more deterministic guidance, which should be watched and could lead to additional changes in later forecast packages. For the moment, triple point emergence has more support next Thursday than Wednesday, which plays into the hands of the 12z ECMWF rather than the 12z UKMET/for the most part the 12z Canadian. Used a combination of the 12z ECMWF/12z GFS/00z ECMWF ensemble mean/12z NAEFS mean to deal with detail issues and uncertainty which led to reasonable continuity (a slightly quicker frontal progression) for a forecast at that range. The grids were derived from the 19z NBM except the QPF, which weighted towards deterministic guidance for realistic amplitudes. ...Sensible Weather... Cooler air from the Arctic remains across the North with high-elevation snow possible over the Brooks Range. Meanwhile, the greatest threat of heavy rain will be focused along the coastal sections and nearby high terrain of south and southeast Alaska and the AK panhandle early to mid next week with the return of an occluded cyclone. Local amounts of 6"+ are possible from this system in the favored topography early and mid next week. Meanwhile, the central portion of Alaska should be sheltered from significant rain chances/amounts. However, with the upper trough across the west and deep layer cyclone moving in from the south, much of the state should be cloudy. Cool air from the Arctic will continue chilly conditions along the North Slope with snowfall possible over the Brooks Range. The polar air is forecast to show limited southward penetration down the west coast but should remain across the North Slope into early next to mid next week. The interior will be mild to warm, with temperatures peaking in the 60s and 70s each day. Roth 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