Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 419 PM EST Sat Nov 16 2024 Valid 12Z Wed Nov 20 2024 - 12Z Sun Nov 24 2024 ...High winds and heavy snow could create blizzard conditions across parts of northwestern Alaska through the middle of next week... ...Guidance Evaluation/Preferences... Forecast spread and uncertainty seems below normal next week in amplified flow. Main impacts will focus with system energies riding on the northern periphery of an Aleutians to Interior upper ridge. This features a midweek enhanced wind and snow event from northwest to northern Alaska and a likely second well organized storm system into next weekend. The 12 UTC GFS/GEFS seem to crash energy too earnestly through the ridge next weekend compared to the rest of guidance, albeit as predictability lowers to average. Deep layered maritime lows dug to the lee of the ridge hold south of the state downstream in this flow. Accordingly, opted to use a 12 UTC GFS/ECMWF/UKMET/Canadian model blend Wednesday into Friday, transitioning to a ECMWF/Canadian ensemble blend next weekend. WPC manual adjustments to this blend were applied to better allow sufficiently deep systems as warranted by favorable upper support to offset inherent weakening due to the blending process. ...Weather/Hazards Highlights... Generally clear and cold conditions across much of mainland Alaska early next week give way to moderating temperatures and increasingly stormy weather for western and northwestern/northern Alaska heading into midweek as an increasingly amplified pattern develops. The cold upper low lingering northeast of Alaska early next week will give way to a strong ridge building from the Aleutians to the Interior. This will be followed by the arrival of an amplifying trough from the west, from which a cyclone is forecast to develop and move through the top edge of the amplifying ridge. The gradient between the strong ridge and the main trough will bring a long fetch of moist southerly flow across the Bering Sea, bringing an increasing threat of high winds and areas of heavy snow into the northwestern mainland through midweek. The combination of the heavy snow and high winds would create blizzard conditions. The snow and winds will likely penetrate farther east across the Brooks Range and the North Slope on Wednesday, with high winds possibly to linger across the North Slope into Thursday behind the departing storm system. Underneath in this pattern, gap wind enhancements may also materialize across the eastern Aleutians and into the southern Alaskan Peninsula. There is also an emerging guidance signal to monitor that another well organized system working into the Bering in this pattern may impact all these areas again into next weekend. Meanwhile, deep layered lows digging to the lee of the upper ridge should provide a lingering maritime threat, albeit held well south of the state. It appears that much of the impactful precipitation associated with this system will mainly pass south of the Panhandle next week. Schichtel 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