Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
770 FXAK68 PAFC 120046 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 446 PM AKDT Sat May 11 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... The low will continue to track slowly to the east-northeast, reaching the northern Gulf tonight, with the occluded front dissipating as it pushes onshore. Winds and precipitation along coastal areas will diminish tonight, with precipitation becoming more showery with time. The upper low will open into a trough as it heads inland across the southeastern Copper River Basin and into the Yukon on Sunday. This will leave a weak trough over Southcentral for Sunday. With a fairly moist airmass in place and increasing instability as some breaks develop in the clouds cover, it looks like a favorable day for some scattered afternoon/evening showers. As is typically the case, expect the bulk of these along or near the mountains. Weak ridging will build overhead on Monday while a weak low tracks south of Kodiak and into the Gulf. Kodiak will see a quick shot of light rain as a low passes through the Southern Gulf. There still could be some afternoon/evening convection in Southcentral, but with a lack of upper level forcing and weak instability expect shower coverage to be more isolated in nature. Temperatures will incrementally warm as we head through the next few days, with increasing sunshine and overall moderation of the chilly airmass currently in place. As the southern Gulf low moves to the east, an upper level trough will phase with the low and push east across Southcentral Tuesday afternoon. This will help to increase the chances for showers along the foothills of the Kenai, Chugach, and Talkeetna mountains and any diurnally driven showers that develop in the Copper River Basin to become more scattered on Tuesday afternoon. For those hoping to get a second chance at aurora viewing tonight, mostly cloudy skies are expected to continue through tomorrow morning. Kodiak looks to be the partly cloudy to mostly clear. Skies will begin to clear a little bit Sunday night and even more so Monday night, but opportunities for enough darkness is quickly disappearing. -SEB/rux && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3: This afternoon through Tuesday afternoon)... Two weaker storm systems move across Southwest Alaska and the Bering Sea through Sunday. Then, a transient ridge provides a short break before a much stronger front begins moving in from the west on Monday. The near-term forecast remains largely unchanged except for a few tweaks to precipitation and thunderstorm potential. The biggest updates were for early next week, to hone in on the strength and timing of the approaching front. Here are the primary hazards we`re monitoring for the next few days: - Flood Warnings and a Flood Watch remain in effect for the Kuskokwim Delta due to ice jam flooding. - Slight chance for thunderstorms this afternoon and tomorrow afternoon across parts of Southwest Alaska. - Gales and light to moderate precipitation for the Bering Sea and Aleutian Islands from Monday through Tuesday afternoon. Diving into the details... of the two weaker systems, one is currently located near Kodiak Island while the other is approaching the Central Aleutians from the south. For the low in the Aleutians, we continue to expect lower impacts, with winds around small craft speeds (25 kt) and light precipitation. There is still some uncertainty with whether precipitation will move far enough north to make it to the Eastern Aleutians (Nikolski, Unalaska, Akutan) tomorrow morning, but any precipitation that does fall will be light. The greater uncertainty with the near-term forecast lies with thunderstorm potential in Southwest Alaska for today and tomorrow. With temperatures warming up into the 50s, a longer duration of daytime heating, and cooler air moving in aloft behind the departing low, we`ll likely see enough thermal instability for convection to develop. The question will be whether this convection will be strong enough and organized enough to produce lightning. The situation for both days looks rather marginal, with the forecast hinging on whether cloud cover will be thin enough to support heating and whether the chaotic array of upper level shortwaves rotating around the Kodiak area low can produce strong enough lift. With radar showing decently robust convection and thinner cloud cover this afternoon, have opted to include a slight chance of thunderstorms in the forecast. Tomorrow does look a bit more favorable for thunderstorms compared to today, especially as weak easterly shortwaves move through and thermal instability increases. While a handful of lightning strikes are not out of the question, the set-up is unlikely to support widespread, prolific, or dry lighting. By Monday, focus shifts to a front extending off a strengthening low that tracks along the Russian coastline. Models are in good agreement that the surface low will bottom out at around 978 mb, supporting a strong front with gale force winds and abundant moisture. This system looks to be unusually strong for the time of year, but warmer temperatures may help to prevent the types of wintertime hazards (heavy or blowing snow) that we typically see with storms of this strength. Instead, the most prominent hazard could be an exacerbation of ongoing floods with onshore flow onto the Kuskokwim Delta coast late Tuesday/early Wednesday. -KC && .LONG TERM FORECAST (Days 4 through 7: Wednesday through Saturday)... For Southcentral... By the long term, south central will be dried out and slowly warming with conditions returning to, or exceeding normal. Ridging over much of the mainland will persist through the end of the week. Clouds will be intermittent across region but some afternoon showers will develop across the Wrangell mountains. By the weekend, clouds and rain will return. A low pressure system will drop down from the northern Bering, south across southwest Alaska and into the eastern Kodiak/Western Gulf of Alaska vicinity. Present forecast guidance keeps this system only precipitating on Gulf communities, though there is a chance the system will shift north, bringing wider spreading rains to the mainland. Overall, temperatures will continue to rise, with daytime highs warming (with no snow). For Southwest and the Bering/Aleutians... The first of two systems will move across the Bering Wednesday and Thursday. This system will drag a front across the Aleutian chain, bringing winds, rain and shifty winds will follow as this tracks east. The brunt of the winds, outside of the Bering, will be be focused towards Bethel into Wednesday evening. The next weather system will develop across the western Bering and move along the Aleutian chain. It is still too early to pin down specifics on the movement of this low a week out, but trends are sliding it south of Bristol Bay by the weekend. && .AVIATION... PANC...VFR conditions will prevail through the TAF period. Southeast winds out of Turnagain Arm will prevail over the Arm early this evening. Winds become light and variable overnight and into Sunday morning. Precipitation with the front lifting to the north Gulf Coast should remain primarily confined to the eastern and southern facing slopes of the coastal mountains along Prince William Sound and the Eastern Kenai Peninsula due to the downslope drying effects of the southeasterly flow. && $$