Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
821 FXAK68 PAFC 240055 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 455 PM AKDT Thu May 23 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Tonight through Sunday)... Low stratus around Cook Inlet mixed out this morning, allowing for some daytime heating to kick off cumulus/rain shower development, especially over the southern Susitna Valley and the western Kenai Peninsula. Isolated to scattered rain showers will continue through the evening until the sun angle becomes too low to support sufficient surface heating. Further east, a weakening front over Yukon and extending into Interior Alaska is producing steadier rainfall north and east of the Wrangell Mountains, for locations including Mentasta Lake, Nabesna, and Chisana. These locations have seen around half an inch of rain since this morning. This rain will taper off through the evening hours and overnight tonight as the front exits to the north and east. The weak ridge contributing to relatively drier, sunnier conditions for most of Southcentral will shift quickly eastward tonight, as a low tracking into southern Alaska from the Bering Sea moves in behind. This will bring cloudier conditions and another round of precipitation to Southcentral into the weekend. Rain chances return for much of the area on Friday, though the heaviest, most persistent precipitation will occur along the north Gulf coast. The front will attempt to move up Cook Inlet on Friday, making rain a near certainty for much of the western Kenai Peninsula, though the front weakens through the day as it pushes north. As a result, Anchorage and the Mat-Su Valleys will likely see much lighter, spottier precipitation. As a triple point low develops along the front in the Gulf on Friday, a weak coastal ridge builds. This will drive southerly winds through the typical gaps, including Turnagain Arm, the Knik River Valley, and the Copper River Valley. The low shifts into the central Gulf Friday night, allowing the coastal ridge to relax and gaps winds to diminish. Cooler air aloft accompanies the low, which will drop snow levels to around 2500 ft through much of the coastal mountains. The main impact will be potential for light snow through Thompson Pass on Friday night. The low`s front lingers along the coast, keeping these areas wet through Saturday, though the low weakens for Sunday, allowing for conditions to dry out. 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. The one exception looks to be an upper-level easterly wave which tracks across the Copper Basin on Saturday, bringing further rainfall. The wave shears apart as it tracks west, meaning much of the precipitation does not look to make it past the Talkeetna/Chugach Mountains, though a chance for precipitation remains. - Quesada && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... A Bering low will continue to move eastward reaching Bristol Bay tomorrow and the Gulf of Alaska Saturday. Frequent rain showers will persist in the Southwest and Alaska Peninsula through tomorrow evening with scattered showers afterward into early Saturday morning. Wet snow could mix in with the rain showers in Mekoryuk-Toksook Bay-Kipnuk area his evening. The heaviest precipitation through tomorrow afternoon is expected in Southwest Alaska. The area of heaviest precipitation will shift southward to the Alaska Peninsula afterward through Saturday morning. Widespread fog could develop this evening into tomorrow morning. Westerly wind gusts along the Aleutians will range from 35 to 45 mph through tomorrow evening before becoming more northerly to northwesterly for Saturday. Cooler temperatures in the Aleutians are also expected as a result of the northerly winds this weekend. Clearing skies are expected with the switch to northerly to northwesterly winds Saturday evening and Sunday in interior Southwest Alaska. A Kamchatka low will bring a front through the western Aleutians reaching Adak as early as Sunday morning. Ahead of this, southwesterly winds will signal a warmer and less cooler period for Sunday in the Central Aleutians. -DJ && .LONG TERM FORECAST (Days 4 through 7) Monday through Thursday... The Alaska Weather Map is under a very broad area of upper level lows, with three separated centers. The first is a weakening center in the Southern Gulf of Alaska/Northeast Pacific that is drifting Eastward. The second is a somewhat energetic center meandering around the Bering Strait. The weakest of the three is a center in the Western Aleutians and Bering. The main focus is along the Southern portions of the state with additional energy that arrives via the North Pacific through the forecast period. The Northern low center contributes to weather producers over Western Alaska. Model confidence is good with a deterministic blend changing over to a one-half ensemble blend by midweek. The end result is an elongated areas of low pressure extending across the Bering into the Gulf for Thursday. Overall looking at a good mix of sunny breaks and wetter weather. Periods of rain spread across Southcentral Alaska to just North of the Alaska Range through Thursday. A well developed front brings locally heavy rain over the Aleutians and Bering, spreading into Southwest Alaska late Wednesday. A second well developed low and front bring another round of locally heavy rain into the Western Aleutians and Bering late Wednesday into Thursday. - Kutz && .AVIATION... PANC...VFR conditions are expected through Friday morning. A slight increase of west to southwest winds from Cook Inlet with the sea breeze could occur through this evening, until about 06Z. Otherwise, light south to southwest winds will prevail. && $$