Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
968 FXAK68 PAFC 290033 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 433 PM AKDT Tue May 28 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... A Prince William Sound low continues to rotate offshore this afternoon. This resulted in the upper level trough to migrate westward continuing to bring north to northeasterly winds into the Copper River Basin and Prince William Sound coastline. An area of precipitation continues to move through Prince William Sound this afternoon. Rainfall amounts from this area of precipitation range from a trace to a few tenths of an inch through 400pm today. The precipitation will continue to migrate southwestward through late this evening. A mix of sun and clouds was today`s theme in the Mat-Su, Anchorage and Kenai Peninsula areas today. The aforementioned trough migrating westward will bring an end to the dry conditions. Overnight, clouds will increase and rain showers become more numerous throughout the region as the area of precipitation moves westward from Prince William Sound. Tomorrow, a front from a low presure system crossing the Bristol Bay will push northward over Kodiak Island and the Kenai Peninsula. This will result in a return of cloudy, rainy and windy conditions for coastal locations. Ahead of the front, moderate easterly winds are expected in Kodiak Island and the Kenai Peninsula overnight through tomorrow afternoon and in Cook Inlet, Passage Canal and Turnagain Arm will increase tomorrow afternoon and evening. Strong gap winds are expected too as the front moves northward through the day. Scattered rain showers are likely in Anchorage and the Mat-Su Valley tomorrow as well. Looking ahead, a Gulf low could bring continued rain to the Gulf coast and Prince William Sound Friday, though there is some uncertainty in how far north this low will make it in the Gulf. -DJ && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3: This afternoon through Friday afternoon)... Unsettled weather continues through the remainder of the work week as two lows move across the forecast area. The most notable weather will be the chance for thunderstorms across Southwest Alaska this afternoon and evening, then winds to gale force and steady rain for the Western and Central Bering/Aleutians from Wednesday afternoon through Friday afternoon. Diving into the details...a weakening 997 mb low is currently located north of Nikolski, where it is bringing showers and breezy conditions across the Eastern Aleutians and much of Southwest Alaska. Multiple upper level shortwaves rotating around the low will lead to spells of more active weather until the low itself exits the area on Wednesday. Of note is the slight chance for thunderstorms in Southwest Alaska today as a wave emanating from this low merges with another shortwave moving in from the east; the combination of thermal instability from daytime highs in the 60s and weak synoptic lift from these waves provide decent support for convection. With southeasterly steering flow, the expectation is for showers (and any thunderstorms that develop) to move northwestward through the evening. The Western and Central Aleutians/Bering Sea will stay relatively quiet, but cloudy, through around midday Wednesday as a transient ridge builds between storm systems. The next system, a 964-970 mb low, begins to push its gale force front into the Western Aleutians by Wednesday afternoon. The low begins occluding on Thursday, with southwest small craft speed winds wrapping around the low. Forecast confidence is decently high with this system. The primary challenges are minor differences in low track and timing, as well as the potential for precipitation along the Eastern Aleutians and Alaska Peninsula to be a higher than currently forecast as a North Pacific shortwave directs moisture towards these areas on Thursday. -KC && .LONG TERM FORECAST (Days 4 through 7) Saturday through Tuesday... An elongated area of upper level troughing continues across the Bering into the Gulf of Alaska. The Gulf low weakens and becomes absorbed by a second center moving across the Southern Bering and Alaska Peninsula by Sunday. The jet stream energy maintains its track to the South of the Aleutians through the beginning of the week. A deterministic model blend hold good confidence through the weekend before an ensemble blend takes over. Weak ridging sets up over the Central and Northern Mainland, as well as over Siberia, which will allow for lower level thermal troughs to form across the Central Interior beginning in the new week. Sustained Easterly to Southeasterly airflow over the Southcentral areas spreads increased moisture as far North as the Alaska Range, and brings showers with each Easterly wave. Potentially larger amounts of rain over the Copper River Basin associated with more convective events are expected. Transient lows, fronts and troughs spread their precipitation over the Aleutians and Bering, and into Southwest Alaska, and the AKPEN and Kodiak Island. -Kutz && .AVIATION... PANC...VFR conditions and light westerly winds will persist through late Tuesday evening. Overnight, the winds will give way to southeasterly Turnagain winds. Forecast conditions remain unchanged, with sustained 15-20 mph winds and 25-30 mph gusts, before weakening into the Wednesday morning. Rain showers will develop late overnight and last into the morning hours as well. Occasional MVFR conditions are possible with any shower activity. && $$