Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
701 FXAK68 PAFC 230057 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 457 PM AKDT Wed May 22 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... Cool and cloudy weather continues across Southcentral Alaska this afternoon as an upper-level low remains situated over Western Alaska. An occluded front lifting across Southcentral this evening will continue to bring moderate to heavy rain along the coast of the eastern Kenai Peninsula and Western Prince William Sound. While it appears, based on radar reflectivities, that some moisture has been overspreading the mountains, only trace precipitation (some light sprinkles) have been observed at the ground from Anchorage north into the Matanuska Valley and southern Susitna Valley. Despite the southeasterly flow, however, some marginal instability in the atmosphere is leading to limited downslope drying. Therefore, further south, a stronger feature - a band of light rain showers lifting slowly up the (western) Kenai Peninsula and southern Cook Inlet today - was able to drop one tenth of an inch of rain in Homer. This feature will lift northward this evening, reaching Anchorage and the Mat-Su Valleys tonight. Similar amounts of rain as seen in Homer today are also forecast for Anchorage, Eagle River, Palmer, and Wasilla. While southerly gap winds through Turnagain Arm, the Knik River Valley, and the Copper River Valley persist this afternoon, they will diminish this evening as low pressure in the northern Gulf shifts east and the current coastal ridge breaks down. Heading into Thursday morning, the occluded front pushes into the Copper River Basin, where limited cross-barrier flow will allow for most places to see some limited rainfall accumulations. Greater accumulations are likely north and east of Glennallen, with over half an inch, up to one inch of precipitation, is possible north of the Wrangell Mountains near Mentasta Lake and Nabesna through Thursday night. Temperatures near freezing at night in the higher elevations mean that snowflakes may be seen down to approximately 2000` with some light snow accumulation towards Isabel and Mentasta passes. For the Cook Inlet region, Thursday appears much drier with ridging briefly moving overhead. While some clouds are likely to linger around the mountains, lower elevations are likely to see mostly sunny conditions. This will be short-lived, however, as a low tracking into southern Alaska from the Bering Sea will bring cloudier conditions and another round of precipitation to Southcentral. Rain chances return for much of the area on Friday, though the heaviest, most persistent precipitation will occur along the north Gulf coast. A front lingers along the coast, keeping these areas wet through Saturday. Further inland, a shift to northerly flow as the low tracks into the Gulf will lead to some drying and breaks in the clouds heading into the weekend. CQ && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... This morning`s precipitation will continue to end this afternoon in Southwest Alaska. A front associated with a Bering low will move through the Western Aleutians this afternoon. It will reach the Pribilofs and Central Aleutians late this evening and the Alaska Peninsula/Southwest Alaska coast early tomorrow morning bringing gusty winds, fog, low ceilings and precipitation. Localized southwesterly wind gusts ranging from 35 to 45 mph in the gaps are expected tomorrow morning into the early afternoon hours in the Central Aleutians with gusts ranging from 20 to 30 mph elsewhere. Precipitation type will begin as rain this afternoon but as colder air wraps around the backside of the front, the precipitation in the Pribilofs, Central Aleutians and points along the northern coast of Southwest Alaska (Kipnuk and Toksook Bay) will be a mix of snow and rain showers this evening and overnight. Little accumulation is expected though. The highest QPF values are expected in the Goodnews Bay to Alaska Peninsula area early to mid-morning tomorrow and in the Kuskokwim Delta late tomorrow morning into the afternoon hours. As the low progresses eastward reaching Nunivak Island tomorrow, another round of precipitation will move through Southwest Alaska from Togiak northward to Bethel tomorrow night before spreading eastward into Aniak to New Stuyahok by early Friday afternoon. Precipitation type is trending mostly rain though a few wet snowflakes could mix in early on for some locations. Trends continue to depict a mostly rain/snow mix for Toksook Bay/Kipnuk areas during this late week event with surface temperatures warming into the lower/middle 30s and temperatures at 850mb only in the 20s. Widespread fog in Southwest Alaska is likely tomorrow evening into Friday morning. Another weak low could move through the Alaska Peninsula Friday night bringing widespread rain showers to Southwest Alaska and the Alaska Peninsula through Saturday afternoon. -DJ && .LONG TERM FORECAST (Days 4 through 7) Sunday through Wednesday... A steadily weakening upper level low slips across the Southern Gulf of Alaska through midweek. A somewhat energetic low in Northwest Alaska transits along the West coast and weakens through the period. A moderate amplitude ridge in the Western Bering flattens out as it moves along the Aleutians by late Monday. Some additional energy moves in with a weak upper low pushing over the Aleutians through Wednesday. Model confidence starts off good in GFS/ECMWF blends and run-to-run consistency, before making the switch to deterministic guidance by midweek. Aside of showery precipitation along the West Coast with the low moving Southward, the bulk of the active weather will come with the surface lows and fronts or troughs over the Southern portions of the state. Areas of rain spread over the Gulf and Southcentral, diminishing through Wednesday. Brief periods of locally heavy rainfall starts over the Western Aleutians and Bering Sunday, moving Eastward into Southwest Alaska, and across the AKPEN and Kodiak Island by the end of the forecast midweek. The next system starts to repeat the weather pattern in the West for Wednesday. - Kutz && .AVIATION... PANC...Winds will once again be the biggest challenge through this evening. Light early afternoon winds have veered southeasterly again as a low in Southwest Alaska has the Turnagain Arm winds bending back into the airport late this afternoon and evening. What should be different tonight is that a front associated with this low should pass through the Cook Inlet region which is expected to shift the winds to a southwesterly direction and diminish them late tonight. When the winds do shift southwest, it will also bring in a period of rain and potentially MVFR ceilings for the late evening through overnight hours. && $$