125 FXAK68 PAFC 040031 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 431 PM AKDT Tue Jun 3 2025 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Tonight through Friday)... A strong shortwave trough lifting across Southcentral Alaska this afternoon is producing moderate rainfall in the Susitna Valley and along the north Gulf coast. Light rain showers also associated with the shortwave lift from the Kenai Peninsula toward Anchorage and the Matanuska Valley this evening, which could lead to around a tenth of an inch of precipitation. A coastal ridge enhanced by this trough is also causing gusty southeasterly gap winds through Turnagain Arm, the Knik River Valley, and Copper River Valley. These winds diminish in intensity this evening as the shortwave lifts north. Tonight, a low tracks approaches Kodiak Island from the North Pacific and heads to the Barren Islands for Wednesday afternoon. This low brings another round of light to moderate rainfall for Southcentral through Thursday. The main front reaches the Southcentral mainland Wednesday morning, with southeasterly flow aloft contributing to a downslope hole extending across portions of the Kenai Peninsula, Anchorage, and north to Palmer. There is some uncertainty in the strength of the downsloping, particularly as a result of how much winds near the surface bend down-Inlet as a result of the low tracking near Kennedy Entrance. A middle of the road solution with winds bending somewhat down- Inlet would lead to light, intermittent rainfall in these typical downsloping areas through the day on Wednesday. Meanwhile, heavier rainfall occurs closer to and over Cook Inlet, much of the Susitna Valley, and along the north Gulf coast. While this would keep southerly gap winds going through the Knik and Copper Valleys, the Turnagain Wind would likely bend mostly out of Anchorage by midday. This solution is also favored because precipitation and thick cloud cover will prevent the necessary heating in the Susitna Valley that would keep the Turnagain Arm wind more neutral or bending north into Anchorage. The low tracks along the eastern Kenai into Prince William Sound for Wednesday night, which will allow southerly gap winds to diminish and become light northerly as the coastal ridge is destroyed. This will also eliminate downsloping and rainfall intensifies/fills in for a short time overnight over the interior Kenai, Anchorage, and Matanuska Valley. In total, expecting around 0.30 to 0.50 inches of rain for these areas, with higher values in the Susitna Valley. Around another inch of rainfall is forecast for Seward with generally south to southeast flow Wednesday through Wednesday night. The Copper River Basin remains dry until early Thursday morning, when downsloping across the central Chugach Mountains diminishes and light rainfall can begin. Some clearing on Thursday over the western Susitna Valley and the Kenai Peninsula could lead to enough instability for isolated thunderstorms. Otherwise, expect the trough to linger over Southcentral through Friday keeping temperatures generally moderated with rain showers possible. However, expect a gradual drying and warming trend through the end of the week. && .SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3: Today through Thursday evening)... A weakening low moving over the Mainland will continue to bring scattered rain showers and continued cloud cover through Thursday evening. High pressure builds in across the Aleutians by Thursday evening. Rain showers were abundant this morning and afternoon as a Bering Sea low continues to move over the Mainland. Twelve hours precipitation amounts through 4:00pm today range from a few hundredths in the AK Pen and Eastern Aleutians to over half an inch across an area from just north of Dillingham northward to Sleetmute. A few breaks in the clouds have occurred from Aniak to Lime Village this afternoon and with cooler air aloft and temperatures in the middle 50s, the likelihood for isolated thunderstorm / lightning development chance remains between 10% and 30%. The same lightning chances exist tomorrow afternoon and evening in this area, too. Northerly then northwesterly wind flow will dominate the Mainland and Aleutians as the low moves into Interior Alaska. This will continue to bring cooler air and keep temperatures in the low to middle 50s throughout the day tomorrow despite peaks of sun through mostly overcast sky. Tomorrow, a weak, fast-moving low south of the AK Pen will bring increased gap winds tomorrow afternoon and evening for the Central and Eastern Aleutians and the Alaska Peninsula with gusts ranging from 20 to 30 knots. In the wake of a third low moving east of the Pribilofs and through Bristol Bay Thursday, high pressure builds into the Aleutians by the end of this week. -Johnston && .LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)... The persistent longwave trough across the Eastern Bering Sea and Aleutians continues to weaken and migrate eastward. Several embedded shortwaves rotating around the main trough axis will track across Alaskan Peninsula, Southcentral and the Gulf of Alaska, which will continue to support cooler and wetter than average weather conditions for the forecast period. High pressure ridges into the Bering Sea through Tuesday. -DD && .AVIATION... PANC... Winds through the TAF period will be generally southeasterly around 10-20 kts. The higher gusts to 40 kt occurring this afternoon should diminish over the next few hours. Expect any rain this afternoon into Wednesday morning to be on the light side, so VFR conditions are expected to prevail through then. However, the rain should become heavier tomorrow morning and could drop ceilings to MVFR. && $$