Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
905 FXAK68 PAFC 250050 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 450 PM AKDT Fri May 24 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Tonight through Monday)... A low in the Gulf of Alaska is pushing a weakening occluded front along the north Gulf coast, bringing rain to much of Prince William Sound and areas eastward. Precipitation associated with this front has been less than previously forecast for locations inland of the coastal mountains, which has allowed for (limited) breaks of sun and the development of rain shower activity across portions of the western Kenai Peninsula and southern Susitna Valley instead. A coastal ridge has also led to gusty southerly winds through the Copper River Basin, while gap winds through Turnagain Arm and the Knik River Valley are expected to pick up this afternoon/evening. These winds relax later tonight as the low shifts into the central Gulf tonight, allowing the coastal ridge to weaken. 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 tonight. The low`s front pulls away from the coast by Saturday, allowing the area to see an end to precipitation likely during the morning hours. Further inland, a shift to northerly flow as the low tracks into the Gulf will lead to some initial drying and breaks in the clouds to start the weekend. Warmer temperatures in the lower levels of the atmosphere will also contribute to high temperatures in the upper 50s to lower 60s for most of the inland lower elevations. This will contribute to an unstable atmosphere which will likely trigger potent rain shower activity in the Copper River Basin and portions of the Susitna Valley Saturday afternoon/evening. An isolated lightning strike or two from a particularly strong shower cannot be ruled out. Southwesterly storm motion combined with upper-level support from a shortwave dropping south across the Alaska Range may allow for some rain showers to push into Anchorage and the western Kenai late Saturday evening into the overnight hours. Then, an upper-level low dropping from south the North Slope will interact with the low lingering over the Gulf and one or more easterly shortwaves tracking in from Yukon. This produces a fairly uncertain forecast for Sunday and beyond, though the combination of features will provide support for rain showers and likely some steadier rainfall at times nudging into the easternmost portions of the forecast area as early as Saturday night. These precipitation features will propagate generally east to west, with the most likely areas to see over a tenth of an inch of rainfall in the Copper River Basin. However, there is moderate potential for this heavier rain to reach the western half of Southcentral late Sunday and heading into next week. Regardless, expect continued generally cool and cloudy weather with the occasional break of sun as well as the occasional shower. -Quesada && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... An elongated trough through the Bering Sea will help to push the Bering Low that has been impacting the region this week into the Gulf of Alaska by tomorrow morning. The widespread effects of this low including gusty winds, rain/snow showers, low clouds and fog, will end overnight into tomorrow morning for most of Southwest Alaska and the Alaska Peninsula from north to south. As the low moves south and east, northerly winds will persist in the Aleutians and coastal areas of Southwest Alaska. These northerly winds will produce scattered rain showers for the northern side of the Aleutians and coastal areas of Southwest Alaska tomorrow. A Kamchatka Low brings its front to Shemya and the Western Aleutians as early as tomorrow morning. Its progression eastward will be slowed as weak high pressure moves into the North Pacific resulting in a ridge over Central Aleutians. This ridge could allow for warming temperatures for Sunday; ahead of the Kamchatka Low`s eastward migration. Weak northeasterly winds are likely tomorrow afternoon into Sunday resulting in interior flow. Model trends the past few days have consistently showed a weak shortwave moving through the Kuskokwim Delta tomorrow afternoon into the evening hours. This wave, aided by breaks in clouds, could result in isolated thunderstorms for Bethel and surrounding areas late in the afternoon into the mid-evening hours. -DJ && .LONG TERM FORECAST (Days 4 through 7) Tuesday through Friday... The long term begins Tuesday with weak deformation and troughing remaining over Southcentral and a transient ridge moving from the AKPen and eastern Aleutians toward Southwest Alaska. The weak troughing over Southcentral will lend to continued shower activity across the region, mainly across the mountains and interior portions of Southcentral. The ridge continues east for Wednesday, helping bring a temporary reprieve to the extensive cloud cover and shower activity. However, the ridge quickly moves to the Alaska Panhandle as the upper-level trough, anchored by an upper- level low and associated surface low, reestablishes itself over the eastern Bering and Aleutians by late Wednesday. The result will be a return to widespread cloud cover and precipitation moving from the AKPen Wednesday afternoon across almost all of the Southern Mainland through Thursday. The broad long-wave trough remains in place with continued unsettled weather and cooler temperatures through the end of the week and into the start of next weekend. - TM && .AVIATION... PANC...VFR conditions are expected persist throughout the TAF period, but occasional dips to MVFR are possible. A frontal system will move up into Southcentral later this afternoon, bringing with it the potential for light rain showers and/or sprinkles to the terminal along with possible ceiling reduction below 5000 ft. Turnagain Arm winds are likely to develop and bend into Anchorage late this afternoon and evening, with southeast gusts up to 25 kts possible until winds diminish later tonight. Winds are expected to diminish by early Saturday morning then shift out of the north. MVFR ceilings are also possible overnight into early Saturday morning. However, confidence is low regarding this solution. && $$