Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
282 FXAK68 PAFC 221238 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 438 AM AKDT Sat Jun 22 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today through Monday night)... The forecast remains mostly on track for the next couple days across Southcentral Alaska. Today will feature a ridge building overhead and a warming trend. High temperatures will generally range from the upper 60s along the coast to 70s and 80s inland. The warming for inland locations such as the Copper River Basin and Susitna Valley will be driven by gusty northerly winds. These winds will also help to lower relative humidities. As such, a Red Flag Warning remains in effect through today for those areas. The complication to the forecast will be the coverage of convection in the presence of the ridge building overhead. Although unstable, the valleys/lower terrain of the Susitna, Copper Basin, Anchorage, and Kenai Peninsula look to remain mostly dry today due to the descending air associated with the ridge. The better chances for showers and storms look to be along the foothills of the higher terrain. However, storm motion looks to be light and out of the northeast, so any storm that does form along the mountains could advect into the valleys. The question remains, if storms do advect into the valleys, can they hold together with relatively drier air in place at the surface, albeit unstable air. The story remains mostly the same for Sunday concerning thunderstorms. The only exception is that temperatures should be a bit lower than today and relative humidities should be a tick higher. The only exception is the Copper Basin which will remain pretty dry for Sunday but with lower winds. By Monday, ridge axis moves eastward toward the ALCAN border with continued warm temperatures expected. Guidance is still having a tough time figuring out if a wave from the west will move over the area or not. While diurnal convection is still anticipated, there is still moderate uncertainty if the storms will become more organized or not. && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA/ALEUTIANS (Days 1 through 3: This morning through Tuesday morning)... The big picture of the forecast remains largely unchanged, though there continue to be updates to the precipitation and thunderstorm forecast for Southwest Alaska. Expect thunderstorm chances to persist through the weekend for Southwest Alaska, along with a general warming trend. For the Bering Sea and Aleutian Islands, most areas will see light winds less than 25 kt except for coastal marine zones south of the Central Aleutians, which will experience winds to small craft speed as a weak low skirts south of the Aleutians. Model agreement remains poor beyond Monday as models struggle with the track of an approaching weak North Pacific low. Diving into the details... rain showers and isolated to scattered thunderstorms revisit Southwest Alaska this afternoon and evening, north to south, mainly on the west side of the Alaska Range. Today`s convection looks to be a bit more robust than yesterday`s, so expect a little more lightning and rainfall. Thunderstorm chances continue through Monday, with forecast confidence slowly improving. Thunderstorms could move out onto the coastal waters of Bristol Bay south and east from Dillingham, so mariners are advised to monitor the forecast for updates. Concerning model uncertainty, there continue to be differences in the projected track of a weak, North Pacific low approaching the Western and Central Aleutians on Monday. The biggest change with this forecast package was to delay the onset of stronger winds and the onset of rain. The forecast may continue to shift as models better focus on this low. Regardless, this weak storm system is unlikely to have major impacts on the Western and Central Aleutians. && .LONG TERM FORECAST (Days 4 through 7: Tuesday through Friday)... A very dynamic weather pattern is continuing to develop across the region. A low over the Sea of Okhotsk, with associated fronts, will track slowly eastward and weaken as it approaches the Western Aleutians producing showers and gusty winds along its path. Its upper level low will merge with the long wave trough that stretches back over the Bearing Sea and into the Kamchatka Peninsula. A North Pacific low south of the Aleutian Islands will slowly progress towards the east and slowly strengthen as it approaches the Gulf of Alaska. This system has the potential of producing locally heavy precip and gusty winds in Western Alaska, Bristol Bay and the Eastern Aleutians. Models are in fairly good agreement in the short term but diverge greatly as the GFS keeps the system south of the Eastern Aleutians and ECWMF speeds things up and has the system centered over Bristol Bay by the end of the period. A well developed low the Northeast Pacific and associated fronts continues to track towards the east and front spreads locally heavy rain and gusty surface winds less than gale force across the region and into coastal Canada with the system dissipating early Thursday. -Kutz/Dellinger && .AVIATION... PANC...VFR conditions will continue to persist through the TAF period. Light and variable winds this morning will become more southerly during the afternoon hours. Southerly winds return to a more light and variable regime tonight and into Sunday morning. The forecast remains on track for the vast majority of showers and convection to remain north of the area in the vicinity of the high terrain of the Matanuska Valley and Copper River Basin. However, there is a possibility that a shower or two and even a storm could make it off the high terrain of the Chugach Mountains and in the vicinity of Anchorage. Confidence and probability remains low regarding this though. Any showers and thunderstorms that do develop will die down overnight with the loss of day-time heating and instability. && $$