Expires:No;;033047 FXAK68 PAFC 091335 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 535 AM AKDT Wed Apr 9 2025 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... Discussion: The upper low that dropped south across Southwest Alaska yesterday has now moved to just east of Kodiak Island of of early this morning. On the south side of this low, an elongated trough is digging across the southern Gulf and North Pacific with models in good agreement with lifting it towards Southeast Alaska on Thursday. Another trough and associated front are rotating around the northern side of the parent low with colder temperatures filtering northward across the northern Gulf behind the aforementioned front. Cold mid- levels has resulted in scattered rain and snow showers over the Gulf with more steady precipitation along the front as it begins to move inland. Cordova has seen a switch to snow this morning as this band moves through. Seward, Whittier, and Valdez are still warm enough ahead of the front for all rain, but as colder temperatures begin to filter in...these locations should also see a change-over to all snow. However, gusty winds moving into Western Prince William Sound may allow for periods of mixed precipitation for Whittier. Depending on how quickly these locations change-over to snow and the showery nature will determine how much snowfall accumulates. But it is looking likely that Seward could see about 2 to 4 inches today as southerly flow develops. Turnagain Pass and Whittier could see around 5 to 8 inches. As the colder air and snow spreads inland across the Chugach Mountains, Portage Valley could see snow accumulations of 6 to 10 inches with gusty winds. While there is some uncertainty in amounts and initial precipitation type at some locations, we have seen over the past few days that these more convectively driven snow bands result in good snowfall rates allowing for snowfall to rapidly accumulate. As such, have gone ahead and issued a Winter Weather Advisory in include Turnagain Pass, Portage Valley, Girdwood, and Whittier for later this morning through Thursday morning. The parent Gulf low will weaken into an open wave tonight as it lifts north towards Prince William Sound. This will allow another round of snow showers the eastern Kenai, Prince William Sound, and the coastal mountains. Thompson Pass could see up to a foot or more of snow through Thursday night. With troughing over western Alaska and the shortwave trough lifting over the northern Kenai and Prince William Sound, expect the ongoing band of snow extending from the southern Kenai Peninsula northward to continue through at least early afternoon. A Winter Weather Advisory remains in effect for the southern Kenai Peninsula this morning. - PP && .SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3: Today through Saturday Morning)... A generally unsettled weather pattern will persist through this forecast period. Conditions will continue to improve along the Alaska Peninsula this morning as a low exits into the Gulf. This will quickly be followed by a shortwave moving across the Bering Sea today, bringing another round of light snow to the Eastern Aleutians and Alaska Peninsula, with the potential for rain to mix with snow as temperatures rise above freezing in the afternoon. Parts of Nunivak Island, Kuskokwim Delta, and Kuskokwim Valley will likely also see some light snow as a weak upper level shortwave moves through. Otherwise, expect clearer skies, lighter winds, and cool temperatures for Southwest Alaska. Forecast confidence diminishes tomorrow night and into Friday as another shortwave trough dives into the Bering Sea from Russia. There's uncertainty with how this trough will interact with an upper low near the Seward Peninsula and, therefore, the positioning of the resultant surface low. The overall impact of this uncertainty is fairly small, mostly affecting the forecast for the Northern to Central Bering Sea, Pribilof Islands, and Kuskokwim Delta. The latest model run of the NAM keeps the surface low in the central Bering, suggesting quieter weather for Kuskokwim Delta. The Canadian model is tracking the system further west over Nunivak Island while the GFS and ECMWF fall somewhere in the middle. We will keep a close eye on how this system progresses going forward. Further south, a North Pacific low and its front skirt the southern side of the Aleutian Chain as it works its way east on Friday, gradually pushing out the ridge of high pressure that sits across the Western and Central Aleutians through tomorrow. There are still uncertainties with the system's exact positioning, which will affect forecast winds and precipitation chances along the Aleutian Chain. A surface low looks to form along the front and track over the Alaska Peninsula early Saturday morning, bringing enhanced winds and precipitation to the region as it moves north into Bristol Bay. -Chen/TK && .LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)... A well developed closed upper low over the Northern Bering begins its sweep across the Alaska Peninsula into the Gulf of Alaska and Eastern North Pacific by Tuesday. This center runs through an elongated negatively tilted trough and slowly weakens through the period. It is also dragging considerable colder air with it. Throw in a number of shortwaves passing over the Aleutians and generally unstable conditions will be spreading from the Central Bering across Southwest Alaska. A generalized blend of forecast models covers the larger scale features, but uncertainty remains high in the unsettled pattern and smaller details. A developing surface low to the South of the AKPEN spread areas of moderate snow and gusty winds from the Eastern Aleutians and AKPEN into the Central Bering on Saturday. The snow will change to moderate rain over the AKPEN and Bristol Bay, spreading over Kodiak Island and along the Southcentral coastal zones as the low gets stronger across Bristol Bay. Winds increase to gale force late Saturday over the Eastern Bering, and through the Barren Islands into Kamishak Bay late Saturday and extend along the Southcentral Coast through Sunday. A weak surface and front push across the Western Aleutians Sunday. Locally moderate snow extends along the West Coast and over the Eastern Bering. As this surface low slips back across the AKPEN, mostly snow remains and slowly dissipates in the West by Tuesday. Moderate to heavy rains move from Kodiak Island into the Eastern Kenai Peninsula, and Western Prince William Sound, diminishing Tuesday. - Kutz && .AVIATION... PANC...Vicinity showers and flurries will continue throughout today with mostly VFR to MVFR conditions expected, accompanied by 5-15 kt southeasterly Turnagain Arm winds. Brief periods of more intense snowfall rates along with IFR to LIFR conditions are not out of the question, but there is also less confidence in exact placement of snow bands that develop. Up to a 0.5" is possible through Wednesday afternoon, while winds shift to light and northerly Thursday morning. -AM && $$