Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 536 PM EDT Fri Oct 18 2024 Valid 12Z Tue Oct 22 2024 - 12Z Sat Oct 26 2024 ...Significant storm to bring heavy precipitation, high winds and coastal flooding threats to West/Southwest through Northern and Interior Alaska into early next week... ...Overview and Guidance Evaluation/Preferences... Latest guidance suggests that predictability remains above normal in the showing a significant storm with long fetch moisture and high winds/waves from the Bering Sea to the Arctic Ocean along with leading coastal flooding, heavy precipitation and high wind threats inland for West/Southwest through Northern and Interior Alaska into early next week. Prefer a composite of well clustered guidance of the 12 UTC GFS/ECMWF/UKMET/Canadian into Tuesday-Thursday. This also acts to trend WPC guidance toward a deeper upstream storm from the Southern Bering Sea to the northern Gulf of Alaska into late next week to monitor. Prefer a composite of best clustered guidance from the GFS/ECMWF and GEFS/ECMWF ensemble means next Friday, before fully transitioning to best compatible 12 UTC GEFS/ECMWF ensemble means into next weekend amid growing forecast spread and uncertainty. ...Weather/Hazards Highlights... The main weather maker continues to be a deep and quite strong surface low lifting from northeast Asia to the Arctic Ocean and its associated trailing 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-west-central 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. This storm will offer a significant maritime winds and waves threat across the Bering Sea and open waters of the Arctic Ocean. Highest inland winds may focus into parts of northwestern Alaska, with the highest gusts expected in the mountains. However, this will present as a widespread high wind threat well inland across the Interior and into the Brooks Range/North Slope with colder snow areas potentially having periods of local blowing snow/near blizzard-like conditions to monitor. Persistent and strong onshore flow may lead to a significant coastal flooding threat as well, with focus also spreading southward through Western and Southwest Alaska. There is also some signal for addional upstream storm development into the Bering Sea in about a week, but at this point guidance uncertainies loom much larger for the potentially organized system that is not about to rival the main lead low. Meanwhile, ample system energies sliding underneath in this pattern across the southern Bering Sea into Southwest Alaska and downstream over the full Alaskan southern tier and northern Gulf of Alaska has now trended more defined and amplified in the next Thursday-Saturday timeframe. This would favor a deeper low pressure system and frontal system to enhance winds/waves and precipitation in unsettled flow. Suspect main inland focus will be from coastal Southwest Alaska and the AKpen to across coastal areas of SouthCentral Alaska to Southeast Alaska. 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