Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 638 PM EDT Wed Oct 16 2024 Valid 12Z Sun Oct 20 2024 - 12Z Thu Oct 24 2024 ...Significant storm to bring heavy precipitation and gusty winds to much of western/northern Alaska into early next week... ...Overview and Guidance Evaluation/Preferences... The period begins Sunday with a shortwave/surface low pressure system moving into the Alaskan Panhandle and Western Alaska with some renewed troughing back along the southern Coast and into the Gulf. A strong upper low over eastern Russia will amplify troughing downstream over Alaska leading to a period of well above normal temperatures. The associated surface low with this deep upper low will move eastward into the Arctic, swinging a cold front through Western Alaska to bring heavy precipitation, gusty winds, and coastal flooding to portions of northwest and interior Alaska around Monday-Tuesday of next week. Behind this, general but weak upper troughing should persist over Alaska into the middle of next week with upper ridging building over the Aleutians and Bering Sea. The latest deterministic and ensemble guidance continues to show very good agreement through the period over Alaska, especially with the deep surface low just north of the state, which only increases confidence in what could be an impactful system for parts of Alaska. There are still some relatively minor timing differences in the front as it swings through the state, and the overall evolution late in the period, but these are details that are hard to resolve at these longer time scales anyways. The WPC forecast for today used an equal blend of the GFS, ECMWF, CMC, and UKMET through Day 6/Tuesday before transitioning to roughly half ensemble means by late in the period to smooth out some of the detail differences. Overall, this maintained very good continuity with yesterdays forecast. ...Weather/Hazards Highlights... The main weather maker will be a strong surface low east of Alaska and its associated cold front as it swings eastward through Mainland Alaska early next week. This system will bring impactful precipitation, mostly in the form of snow especially for the mountains and farther interior, but western areas may see periods of heavy rainfall. Models continue to show the potential for more than a foot of snow for the western and central Brooks Range. Gusty winds are also likely for parts of northwestern Alaska, with the highest gusts expected in the mountains. Persistent onshore flow may also lead to a coastal flooding threat as well. Following a weekend of near to below normal temperatures, warm air advection ahead of the strong storm system is expected to result in much milder conditions by next week, with daytime highs 10-20 degrees above normal for some locations from western to central and northern Alaska Monday-Wednesday. Southeast Alaska should be exception remaining below normal through the entire period underneath persistent upper troughing. Santorelli 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