FXAK68 PAFC 051238 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 438 AM AKDT Thu Aug 5 2021 .ANALYSIS AND UPPER LEVELS... The longwave pattern features a trough over the Bering and North Pacific with a dome of high pressure anchored over Northwest Alaska. At 500 mb there are a series of shortwaves from south of Cold Bay to Bristol Bay and the Y-K Delta. A convective complex formed last evening and numerous lightning strikes were observed between Sleetmute and Port Alsworth. Over the North Pacific on satellite imagery (CIMSS MIMIC PW) there is a well-defined fetch of modified tropical moisture that extends to the Shumagin Islands, across the Alaska Peninsula and into Bristol Bay. && .MODEL DISCUSSION... Model solutions are in sync regarding the longwave pattern and the placement of the major synoptic features. The main forecast challenge continues to be the timing and evolution of the next round of cyclogenesis for Kodiak and the West Gulf. && .AVIATION... PANC...Overall, expecting VFR conditions and light winds. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today through Saturday night)... Areas of low clouds and fog will settle in early this morning from the western Kenai Peninsula to Anchorage and the southern Mat-Su thanks to a low level inversion and radiational cooling overnight. Surface and low level winds are light, so will have to wait for the sun to burn this off. Thankfully, it looks shallow, so expect improving conditions by late this morning. Otherwise, weak ridging will persist over Southcentral, with weak short-waves tracking from east to west across the Copper River Basin. Isolated to scattered showers will focus initiate along inland mountains, then track slowly off the mountains. This pattern will remain in place through Friday, leading to similar weather. More significantly, a strong short-wave trough will track toward Kodiak today, leading to a deepening surface low over the southern Gulf and development of steady rain across Kodiak Island mid to late this afternoon. An upper low center will develop above the surface low tonight, ultimately driving the trough eastward across the Gulf. Rain will continue in Kodiak overnight, then taper off Friday morning. A remnant upper trough will then lift northward across Southcentral Friday night through Saturday morning. The biggest impact to Southcentral will be an increase in cloud cover and cooler temperatures. Weak forcing will once again favor the mountains for showers, while upslope flow along the Alaska Range will lead to a chance of steady light rain. This trough will push the upper ridge off to the east and allow the long-wave trough centered over the Bering Sea to shift eastward and encompass all of southern Alaska by late Saturday. Deep southwest flow with short-waves ejecting out of the long-wave trough is a wet pattern for most of Southcentral. While Saturday will start out fairly dry, expect rain to gradually develop across the region Saturday afternoon through Saturday night as a potent upper low approaches from the west. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)... Unsettled but fairly benign weather will continue across Southwest Alaska over the next couple of days. A nearly stationary frontal boundary is bringing rain to the Kuskokwim Delta and Bristol Bay today. Areas of marginal instability over the northern Kuskokwim Valley will be the areas with the best chance for wet thunderstorms this afternoon. The front will gradually move out of the region tonight into Friday morning. However, lingering showers will continue on Friday and Saturday. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)... Unsettled weather continues over the next few days as the energy from a low in the northwestern Bering Sea becomes absorbed into a second low moving northeastward across the eastern Aleutians on Saturday. There is a chance for a small area of gale force winds near the low center in the eastern Bering Saturday night. Otherwise, winds will remain below gale force with no high seas expected. && .MARINE (Days 3 through 5: Saturday through Monday)... Forecast confidence is fair to low for Saturday and Sunday. Low pressure across the Southern Bering moves into the Eastern Bering by Monday. Gusty winds less than gale force along the Eastern Bering front, with areas of gale force winds wrapping the low for Sunday. Gale force gap winds are possible over the Eastern Aleutians and near channeled terrain on the Alaska Peninsula through Sunday. High pressure over the Gulf yields to a front on Saturday. Gusty winds less than gale force spread across the Western Gulf for Saturday, diminishing. A second low and front South of the Alaska approaches the Southwestern Gulf for Monday. && .LONG TERM FORECAST (Days 3 through 7: Sunday through Wednesday)... The upper low over the eastern Bering could bring widespread rainfall across Southwest and Southcentral on Sunday and Monday. GFS, GEM and ECMWF share similar solutions by keeping the upper low near Bristol Bay through at least Monday evening, while a couple of isolated shortwaves ride past the upper low through the Alaska Range and Southcentral into Tuesday morning. At surface level, models are not quite aligned yet with the next North Pacific low which could bring strong winds by early next week over the Gulf. GFS entertained gale winds to move up the Gulf as early as Monday evening, but the rest of the models pretty much reduced the winds as the low treks toward the western Gulf on Monday afternoon. There's a lot of uncertainty with the latter system as most surface models remain skeptical of the placement and strength of the expected low. Overall, rain and gusty winds along the gaps and passes for the eastern Aleutians, Southwest and Southcentral will likely remain in the long term forecast. Hence, it will be a relatively quiet forecast period should the North Pacific low altered course or dissipated. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...NONE. FIRE WEATHER...NONE. && $$ SYNOPSIS AND MODEL DISCUSSION...PJS SOUTHCENTRAL ALASKA...SEB/CQ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED MARINE/LONG TERM...CB