Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
809 FXAK68 PAFC 060033 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 433 PM AKDT Wed Jun 5 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today through Friday night)... Following yesterday`s fun in the sun, Anchorage had record setting rainfall today, with a rainy day had across most of Southcentral. Driving this pattern shift is a low pressure system in the northern portion of the Gulf of Alaska, spinning multiple waves of moisture in from the southeast. A series of short-waves are rotating around the north side of this low, with areas of moderate rain embedded within the larger area of light rain. As such, rainfall is likely to continue for coastal Southcentral, but slowly begin to taper off in Anchorage this evening. High and low temperatures to be slightly cooler across Southcentral than yesterday given the widespread cloud cover. Looking forward, the Gulf low is weakening as it tracks to the north Gulf coast tonight, with the upper center opening up into a trough. Models are coming together regarding a more northern system, raising the confidence on gusty winds through the gaps tomorrow and continued rainfall across the northern Gulf coast. As the upper low approaches Southcentral tonight the short-waves bringing all of the rain today will begin to exit off to the north and west. Precipitation over Southcentral will diminish and become more showery in nature. What is certain is that strengthening onshore flow behind the remnants of the low will lead to widespread precipitation along the north Gulf coast and Prince William Sound regions through Thursday. Further inland on Thursday, in the Susitna Valley, conditions are looking favorable for some isolated thunderstorm development. Biggest key and uncertainty currently is to what degree the skies scatter out before peak- heating, allowing for the most optimal conditions for development. Gusty southeasterly gap winds are expected Thursday as the pressure changes associated with the passing trough and marginally warmer inland temperatures will amplify gusty wind potential. The last of the short-waves will exit northward Thursday night into Friday, with a weak short-wave ridge building overhead. Thus, expect precipitation to taper off (lingering longest along the eastern Kenai Peninsula). Friday looks like it could be a nice day, with abundant sunshine and temperatures rebounding back into the 60s for most areas. Weather for Kodiak Island will be quiet the next couple days, as they are situated away from the key features discussed above. Guidance is in good agreement that a deep low will lift out of the base of the long-wave trough and track up to the Gulf Friday night/Saturday. This would bring a return of rain and wind to Kodiak as early as Friday evening. -CL/SEB && SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... An arctic upper level low continues to dive south through the Bering into the Central Aleutians through tonight, with scattered snow showers expected to persist across the Pribilof Islands through tomorrow morning. Further south across the central Aleutians, showers with mixed precipitation will continue through tomorrow as the upper level low meanders over the Aleutian Chain. As an upper shortwave swings around the base of this trough, a surface low/low complex will form near/over the eastern Aleutians and swing westward between the Central Aleutians and the Pribilofs through tomorrow. This new surface low will draw notable North Pacific moisture northward with persistent showers expected across the eastern Aleutians and Alaska Peninsula Thursday afternoon through at least Friday afternoon. Any remaining snow showers however will transition to rain showers and will persist for at least a few more days as the upper low remains nearby and the cold airmass slowly moderates. As for Southwest Alaska, scattered showers with mixed precipitation continue across the Kuskokwim Delta through late this evening. Meanwhile, widespread light to moderate rain showers continue to move over the Western Alaska Range and may make it as far west as Sleetmute tonight through tomorrow morning. A few isolated thunderstorms are also possible for the western Alaska Range late Thursday afternoon/evening as a few easterly waves move through with marginal instability. There is still some uncertainty with the location and timing of any convective initiation as there is still disagreement on the location and timing of these weak upper shortwaves. High temperatures for the Pribilofs and Aleutians will struggle to make it out of the upper 30s to lower 40s over the next couple of days. High temperatures for Southwest Alaska however will trend warmer with highs climbing into the 50s and 60s by this weekend. -ME && .LONG TERM FORECAST (Days 4 through 7) Sunday through Wednesday... The Alaska Weather Map is becoming a bit busier through the forecast period. A dual centered upper level low in the North Pacific merges to form a single closed low in the Gulf of Alaska by midweek. An upper level ridge on Sunday moves across the Bering and flattens out for Wednesday, as a well developed surface low moves out of the North Pacific. A new low out of Siberia pushes its way into the Bering, settling into the Central Bering by Wednesday. A broad ridge remains over the Northern two- thirds of Mainland Alaska, and continues its support of surface thermal troughs. Forecast confidence remains good through the period, starting with a deterministic blend before changing to a UK/EC ensemble means. The upper level low in the Gulf hooks up with a North Pacific surface system to spread considerable rainfall across the Southcentral areas from the Canadian Border, across Prince William Sound and the Eastern Kenai to Kodiak Island and parts of the Alaska Peninsula for Sunday and Monday. Mostly offshore gusty winds will occur over the Gulf, but move over Kodiak Island and the Southern Kenai Peninsula through early Tuesday. Unsettled conditions will linger across Southcentral, bringing showers over the area. Transient systems will bring locally heavy rains over the Aleutians and Bering through Wednesday. -Kutz && .AVIATION... PANC...A strong trough moving west of Anchorage will continue to bring rain to the terminal through early evening. Ceilings and visibility are expected to remain VFR, but a temporary reduction to MVFR later this afternoon is still possible in heavier rain. Expect turnagain arm winds to persist over the terminal through late this evening, with gusts to around 25 kts possible at time. Conditions will improve overnight with winds diminishing. The Turnagain Arm winds will redevelop and move back over the terminal by around noon tomorrow with gusts up to 30 kts possible. && $$