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Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
244 FXAK68 PAFC 220108 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 508 PM AKDT Fri Jun 21 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Tonight through Monday)... The low south of the Gulf of Alaska is drifting southward which has allowed a ridge to build over the Kenai Peninsula, Anchorage and eastward along the north Gulf coast. However, an unstable air mass is descending into Southcentral with showers and thunderstorms expected to develop along the Alaska Range and drift southward through the evening. Saturday will see some clearing for the morning, but temperatures will get quite warm over much of the area with widespread 70s and the portions of the Susitna Valley reaching into the lower 80s expected. With this unstable airmass entrenched over Southcentral, the warm day will kick off more widespread showers and thunderstorms across the area. These storms should initiate over the mountains with some of them drifting southwestward to lower elevations after they develop. Sunday will see a similar pattern though temperature should be a tick lower than Saturday. Some of the warming Saturday will be driven by gusty northerly winds. The strongest winds are expected to be across northern portions of both the Susitna Valley and Copper River Basin. With very warm temperatures and low Relative Humidity values, a Red Flag Warning for fire weather conditions has been issued for these areas for Saturday. Monday will see continued warm temperatures with afternoon and evening showers and thunderstorms. There is a little more intrigue as well as models are trying to figure out whether there will be a weak 500 mb wave that moves close to the area from the west or if the upper level ridge will strengthen and re-establish itself at that time. It still looks overall like diurnal convection, but this could become more organized from this wave, or the ridge could win-out and suppress the storms so there is more uncertainty for Monday. && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA/ALEUTIANS (Days 1 through 3: This afternoon through Monday afternoon)... 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 ekes by south of the Aleutians. Model disagreement increases by Monday as models struggle with the track of yet another weak North Pacific low. Diving into the details... rain showers and isolated to scattered thunderstorms are once again moving across Southwest Alaska this afternoon and evening. Today`s convection looks to be a bit less robust than yesterday`s, so expect a little less lightning and rainfall. The major change from yesterday will be storm motion; with the steering flow shifting northerly, expect storms to move approximately north to south today. Thunderstorm chances continue through the weekend, with forecast confidence slowly improving for Saturday and Sunday afternoon. There continues to be potential for thunderstorms to move out onto the coastal waters of Bristol Bay, so mariners are advised to stay weather aware this weekend. Otherwise, shower and thunderstorm coverage gradually shift eastward and temperatures climb as we head into the weekend. Circling back to the model uncertainty, there have been major shifts 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 attempt to better hone in on this low. Regardless, this weak storm system is unlikely to have major impacts on the Western and Central Aleutians. -KC && .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 persist through the TAF period. Winds will become light and variable overnight before picking back up out of the south on Saturday evening. Can`t rule out a few showers or even a thunderstorm moving off the mountains into the area, but the probability remains very low. && $$