Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
976 FXAK68 PAFC 011343 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 543 AM AKDT Sat Jun 1 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... A vertically stacked occluded low over the central Gulf of Alaska will slowly retrograde to the west, reaching an area of the western Gulf south of Kodiak Island Sunday. Its occluded front will remain draped over the northern gulf through the weekend, producing steady rain and easterly gales across the northern Gulf over to Kodiak Island through Sunday morning as a series of upper-level waves and vorticity lobes move along the front. Steady shower activity will also continue along the immediate Southcentral coast, especially across the higher terrain of the eastern and southern portions of the Kenai Peninsula. Farther inland across Southcentral, clouds and showers will be on the increase as an upper-level shortwave out ahead of the occluded front moves from the northern panhandle of Alaska inland over the Copper River Basin and Susitna Valley. The increase in clouds and scattered shower activity will keep temperatures a few degrees cooler than what was observed Friday across interior Southcentral. Conditions across Southcentral are expected to improve, with clearing skies and warming temperatures, for Sunday as the low over the western Gulf slides a bit farther south. This jog southward will allow a ridge to push into the interior of the Southern Mainland. For Kodiak Island, the low, coupled with an advancing inverted trough, will allow showers and gusty winds to persist into Monday. By Monday, the inverted trough and associated easterly upper-level wave will move into the eastern half of Southcentral with another round of scattered showers likely from the Copper River Basin Monday morning into the Susitna Valley by Monday afternoon. && SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... Nighttime microphysics satellite imagery shows the continued presence of a broad upper low across the southern Bering, closely centered over the Central Aleutians, along with a second low located over the Gulf of Alaska, its front crawling westward and encroaching into the Western Alaska Range. Unchanged, high pressure over western Canada extends into interior Alaska. Let`s begin with the Bering low first. This low has occluded and its front is now pushing eastward toward the coast of Southwest Alaska. The presence of the Bering low is promoting widespread cloud cover, a mix of low stratus and fog. Saint Paul has flirted with 1/2 mile visibility through the morning hours. Over the next 24 hours a passing shortwave trough south of the Aleutian Chain is forecast to pick up the Central Aleutian low and carry it into the North Pacific through midday Sunday. High pressure will briefly set in over the southern Bering with drier conditions expected to become more common through Monday. Unsettled conditions are forecast across Southwest Alaska. Morning radar shows rain has spread across much of Greater Bristol Bay. An area of enhanced lift has likely helped with the development of rain as upper level forcing spreads inland from the Bering, and additional lift moves in from the Gulf of Alaska side. Significant degradation of the Bering low is forecast as it moves into the North Pacific over the next 24 hours. Thus, any shower activity on Sunday and Monday will be driven by easterly wave activity from low pressure over the western Gulf. Models are in good agreement with bringing the next wave southwestward across the western half of the Greater Bristol Bay area early Sunday morning. Additional easterly waves will serve to further enhance rain activity Sunday into Sunday night, with much of the Lower Kuskokwim Valley to also experience a round of precipitation Sunday night into Monday morning. The biggest questions for Southwest Alaska entail the potential for thunderstorms Saturday afternoon as well as Sunday afternoon. Any clearing that develops on either day will help promote at least weak instability. The most favorable location for lightning on Saturday will exist north and northwest of Dillingham later this afternoon and evening. Sunday`s thunderstorm chances spread northward from both sides of the Kuskokwim Mountains into the Middle Kuskokwim Valley. && .LONG TERM FORECAST (Days 4 through 7) Tuesday through Friday... A broad upper-level trough over the Gulf of Alaska will continue to persist through Wednesday evening, producing easterly waves that will carry over Southcentral. As showers form from these waves, precipitation totals will mostly be light. However, as increased convective activity is currently expected over the Copper River Basin through midweek, higher local amounts of rainfall are possible with this system. The biggest chance for widespread and heavier precipitation will be Tuesday into early Wednesday as the majority of easterly waves will pass over the region at that time. The trough will start to dissipate and merge with a new trough in the eastern Bering and Aleutians Wednesday night. Widespread showers will be possible over Southwest as the trough lingers over the Bering and slowly moves westward through the remainder of the forecast period. Stronger winds will not be a major concern since the low will be vertically stacked and past its peak intensity. The track of the trough by Friday and into next weekend becomes a bit more uncertain with current model guidance. Some models are suggesting that the trough lingers over the central Aleutians while others shift it much further south and east well outside of the forecast region. -BS && .AVIATION... PANC...VFR conditions and light winds will persist. VFR conditions and light winds will persist through early afternoon. Gusty winds are expected to pick back up out of the south from Turnagain Arm by the early afternoon. These winds will likely persist through late evening before diminishing again overnight. && $$