


Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
770 FXAK68 PAFC 181251 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 451 AM AKDT Sat Oct 18 2025 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: This afternoon through Monday evening)... An upper-level trough is currently stationary over the Copper River Basin this morning. Situated at the base of this trough, a compact vertically stacked low is spinning just north of Montague Island. This feature, combined with lift and cold air advection in association with the larger trough, is driving moisture across the Sound northward into the western half of the Copper River Basin. This moisture is wringing out in the form of snow across the western and northern portions of the valley, with the heaviest snow, on the order of 2 to 4 inches, falling along the Glenn Highway west of Glennallen. Farther west, colder and drier air is spilling south through the Susitna Valley. Lingering moisture along the foothills of the Chugach and Talkeetna Mountains is resulting in areas of fog and low stratus from Willow south to East Anchorage. The aforementioned compact low will move south through this morning as the larger upper-level trough slides east toward the Al-Can border. As it does, the snow will taper from east to west across the southern Copper River Basin, but not before an expected snowfall total of 2 to 6 inches, with the highest amounts around Eureka. The combination of the low moving south, cold air advection, and a ridge of high pressure building over the interior, will drive gusty gap winds out of Seward, Whittier, Thompson Pass, and the marine zone complex of Valdez. While gusty northern gap winds through Thompson Pass and Valdez Narrows persist into Monday, northerly surface flow should inhabit really gusty conditions from getting into Whittier by Sunday. A light easterly component is even possible for Passage Canal/Whittier Sunday as the pressure gradient reorients. Whittier winds and Passage Canal winds look to pick back up from the west on Monday as a front lifts towards the Gulf Coast by then. Speaking of the aforementioned front lifting towards the Gulf Coast for Monday, the parent low pressure to this front continues to trend more northward compared to previous model runs. As a result, Kodiak Island will be wetter and windier Sunday night into Monday with most of the heavy rain being confined to the Gulf waters. Rain looks to also reach the Eastern Kenai Peninsula and Western Prince William Sound Monday morning with rain perhaps clipping portions of the northern Gulf Coast as well. The strongest winds still look to remain on the southern flank of this system in the North Pacific with some gale-force gusts over the Gulf waters; however, easterly gales are also looking more likely along the front as it lifts into the northern and western Gulf. This system moves to the eastern Gulf and Southeast Alaska by Monday evening. Stay tuned to further forecast updates as details become more clear regarding this next frontal system for Sunday and Monday. -TM/DAN && .SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3)... As of this morning, a surface trough is situated from northwest- southeast across Unalaska and King Cove as a surface ridge slides eastward across Southwest Alaska. A compact low looks to develop within the trough envelope and bring showery and breezy weather to the Pribilof Islands through this afternoon. Meanwhile, farther west, weak transient ridging across Adak and Amchitka is eroding away as a 1007 mb occluded low and its front move eastward and away from the Western Aleutians. The global models have trended a bit northward with the advertised deep North Pacific low, which in turn will nudge and bring easterly/northeasterly small craft and gale force winds closer to Atka, Nikolski, and Unalaska for this evening into early Sunday morning. If the current guidance holds / or keeps trending northward, these winds will expand in coverage Sunday morning. Likewise, confidence has increased that rainfall begins this afternoon for these areas through Sunday morning as the northern most portion of the low`s precipitation shield sideswipes the Central and Eastern Aleutians. With high pressure taking center stage across Southwest Alaska Sunday morning, clearing skies and decreasing winds will allow for some coastal and interior valley locations to bottom out in the low to mid 20s for overnight lows. As the aforementioned surface low tracks south of the area and deepens, its upper level low component will amplify the 500 mb pattern, allowing for upper level ridging to build in from the southeast. At the surface, cold air advection from the light northerly to northwesterly flow looks to be roughly on par with some of the coldest air so far this season for the region. As the surface low tracks just south of the Aleutians and Alaska Peninsula through Sunday afternoon/evening, northwesterly winds in its wake will act to reinforce cooler temperatures across Southwest Alaska. Meanwhile, a secondary low pressure system works across the Western Aleutians Sunday afternoon, bringing another round of rain and windy conditions. As the low moves eastward towards Adak and Atka, the global models have the system weakening and evolving into a complex low as the 500 mb pattern becomes increasingly de- amplified and flatter through Monday morning. The latest runs of the GFS, EURO, and Canadian all show a potent upper level wave and closed low drifting southward from the Bering Strait and over Southwest Alaska Tuesday morning. There are subtle differences in timing and placement of this feature, and the GFS currently wants to develop a surface low Tuesday evening. This will be one to watch for potential precip chances mid week. -AM && .LONG TERM FORECAST (Days 4 through 7)... Upper level troughing over Mainland Alaska and a broad surface low in the western Gulf of Alaska early this week will progress into the eastern Gulf of Alaska through midweek. While relatively good model agreement indicates most energy and associated rainfall with this system will be directed towards southeast Alaska, periods of rain can still be expected along the immediate coast for the eastern Kenai Peninsula and Prince William Sound as several weak perturbations rotate north into the northern Gulf Coast. Eastward progression of this storm in the Gulf will promote gusty northwesterly winds across the AKPen for Wednesday into Thursday, with a cooler airmass spreading across the Bering and much of the Mainland. Guidance points to the jet stream becoming more zonal in the North Pacific and in the Gulf of Alaska late in the week. Multiple areas of weak low pressure across the Bering Sea, North Pacific, northern Gulf of Alaska will keep much of the region under a generally showery regime. Exact placement of these lows remains uncertain and inconsistent, but confidence remains moderate that the pattern remains rather progressive in the zonal flow. && .AVIATION... PANC...Predominantly VFR conditions and light northerly winds are expected through the TAF period. There is a chance for a brief period of MVFR conditions and patchy vicinity fog are possible early this morning. && $$