Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
876 FXAK68 PAFC 060141 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 541 PM AKDT Sun May 5 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... A broad trough of low pressure exists over much of the Gulf with weak ridging poking in over the AlCan border. To the west, an area of upper level diffluence has set up over Bristol Bay. The main weather feature for the next 24 hours will be an easterly wave currently moving over the Copper River Valley that will move west over the remaining portions of Southcentral. This will overspread precipitation as it moves east and interacts with the area of diffluence. Guidance also indicates a deformation band setting up somewhere from the southern Mat-SU south to the western Kenai Peninsula. The main uncertainty in the forecast is how the easterly wave will interact with the diffluence and where the deformation sets up. This forecast package reflects a band that will move east from the Mat Valley and Anchorage area in the early morning, moving east to the western Kenai and Susitna Valley later in the morning to afternoon hours. Most areas are looking at .1 to .3 inches of precipitation, but should this band stall over an area, or the convection tonight be more intense, totals near 0.5 inches can be expected. Moving into Tuesday there are no discernible, stronger features, so afternoon showers near the terrain can be expected, with higher chances along the coast and PWS with onshore flow. Some breaks in the clouds may also lead to warmer temperatures in spots. On Wednesday a compact low will move near the Gulf coast and PWS, leading to steadier precipitation for coastal communities and otherwise drier conditions inland. - CJ && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE SEA AND THE ALEUTIANS (Days 1 through 3)... Scattered rain and snow showers will continue through mid-week. Freezing spray, heaviest just south of the ice shelf from St. Matthew Island to Nunivak Island and northward, is expected today into tomorrow evening. An Arctic High will cause northerly winds through the Bering Strait this evening through tomorrow afternoon. Tonight`s push of cold air is expected to be most prevalent along coastal areas of the Kuskokwim Delta southward to the Alaska Peninsula and along the Bristol Bay coast. Persistent onshore winds will keep tonight and tomorrow`s temperatures below normal under a mostly cloudy sky. Tuesday morning, low pressure from the Bering Strait will bring a reinforcing push of cold air southward to the Alaska Peninsula and Aleutians by the evening hours. This low will join a weaker one near the Pribilofs Tuesday. Strong northerly winds from these lows joining will result in heavier snow and rain showers for areas west of Dutch Harbor. Current models track the joined low southward through the Central Aleutians later in the week. -DJ && .LONG TERM FORECAST (Days 4 through 7: Thursday through Sunday)... Broad troughing stretches from the western Aleutians towards the Gulf of Alaska, with multiple surface lows tracking across the Aleutians and into the Gulf. Precipitation along coastal regions of Southcentral, including Kodiak Island, will persist through much of the long term. Some precipitation will likely spill over into Southwest Alaska as the Gulf low moves over the Kenai Peninsula on Thursday. Since the low developing out near the Western Aleutians on Thursday stays south of the Aleutians as it travels towards the Gulf, precipitation will likely diminish over Southwest by late Friday. An upper-level ridge attempts to build through the weekend across portions of the Bering and Aleutians, however, each model solution shows differences in the way the ridge interacts with the surrounding lows/troughs. && .AVIATION... PANC...While the Southeasterly winds out of Turnagain Arm are expected to develop again by early evening, one difference is that they will likely not diminish much overnight, but stay over the airport overnight and through the day on Monday. This is due to an upper level short-wave that will move in from the northeast overnight though Monday morning. It is looking more likely that this wave will also bring in rain from late tonight though Monday morning. Ceilings and visibility will drop near MVFR levels and may go MVFR for a time. && $$