Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
300 FXAK68 PAFC 271326 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 526 AM AKDT Mon May 27 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today through Wednesday Night)... A wet morning is underway across much of southcentral Alaska. As of 5am, radar imagery shows a band of precipitation stretching from approximately the Talkeetna Mountains and northeastern Susitna Valley southwards through the Anchorage and portions of the western Kenai Peninsula. Farther east, a potent shortwave trough on the northern periphery of a low parked across the Northeast Pacific is bringing precipitation to areas along the Gulf of Alaska Coast, as well as much of the Copper River Basin. Overnight rainfall observations show around a tenth of precip for much of Copper River Basin and about a tenth or two across much of the eastern Susitna Valley south through Anchorage. The winners overnight have been the Palmer area and also McCarthy, both of which picked up in excess of 0.30". Precipitation across the east will continue through much of the day, with the heaviest precipitation focused along an axis along and east of the Richardson Highway. Farther west, the current band of precipitation is expected to gradually pivot and diminish as the day progresses. Should enough breaks in cloud cover occur, heat-driven instability may spawn a few showers, particularly across the northern Susitna Valley where breaks are most likely. As we head into midweek, much of the same is expected... though admittedly this becomes a rather difficult pattern to diagnose. Southcentral Alaska will continue to sit in an area just north of an upper-level low and then troughing in the Gulf of Alaska w/ several upper-level waves propagating westward from Yukon. Strong waves will bring more stratiform rain and consistent cloud cover, but weak waves and the edge of stronger waves may result in breaks in clouds, but also daytime instability and possibly showery precipitation. In any case, the Copper River Basin and surrounding area (eastern AK range, eastern Chugach, Wrangells) will be in a rather active and potentially wet pattern for days to come. The Susitna Valley south through Anchorage and the Kenai Peninsula are much more uncertain, but some rain-making mechanism will be possible each day. Forecast certainty is a bit higher for Kodiak Island where some isolated showers are possible today and Tuesday, but then widespread and steady rain is likely for Wednesday as a front pivots into the island from the southwest. -Brown && .SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS (Days 1 through 3)... Southwest Alaska is expected to remain dry for yet another day as weak high pressure ridges inland from the eastern Bering. This will also promote mild winds over the region today and tomorrow. Morning satellite imagery shows continued low stratus and fog situated over the Bering with a small area of clearing located over the Kuskokwim Bay down and offshore of the Nushagak Peninsula. A broad front extends southeastward from the western Bering into the Eastern Aleutians. This front is bringing showery conditions and an axis of southeasterly winds gusting between 25 to 30 knots. This axis of wind and rain will spread east through this afternoon, reaching Nikolski later this morning and Unalaska this afternoon, before stalling and slowly weakening. Into Tuesday a surface low is forecast to develop along the front somewhere immediately north of the Eastern Aleutians. Enhanced southeasterly flow will become more prominent through the Alaska Peninsula with increased gap winds out of the usual locations. Across Southwest, a shortwave trough lifting out of the North Pacific will promote renewed shower chances from Bristol Bay into the Lower Kuskokwim Delta and Lower Kuskokwim Valley. While thunderstorm chances are less certain, it appears isolated wet thunderstorms will be possible with an area of weak instability developing over the Middle Kuskokwim Valley late in the day. Any activity that does develop should get carried northwestward within broad southeasterly flow aloft. By Wednesday a surface low over the Eastern Aleutians will begin to weaken and fall apart. Shower activity and winds over the Alaska Peninsula should gradually diminish over the course of the day. The Aleutians and Southwest should experience below normal temperatures while the low remains as well as general cloudiness. -BL && .LONG TERM FORECAST (Days 4 through 7) Thursday through Sunday... By Thursday, a low pressure system will center itself near the Alaska Peninsula and stay situated until midday Friday. Widespread precipitation across Southwest is possible until a deep upper- level trough enters the Western Bering on Friday and causes the low to dissipate. The new trough will traverse across the Aleutians through the weekend before ending up near the western Gulf of Alaska. The exact trajectory of the system is still unknown, with some models keeping the trough north of the Aleutians through Sunday morning and other models pushing it south as early as Saturday. Over Southcentral, easterly flow will persist into Friday afternoon as ridging continues to build in from Western Canada over mainland Alaska. This will help support the formation of afternoon showers as easterly waves and increased instability build up over the course of the week. Weaker troughing will persist over the Gulf through the forecast period until the upper level trough from the Aleutians enters the Gulf. Model guidance is suggesting a compact shortwave low could form and impact parts of the northern Gulf Friday afternoon and evening. The low is expected to dissipate over the Gulf by Saturday, but the exact location is still unknown. The upper-level trough from the Aleutians entering the Gulf on Sunday will provide unsettled weather for most of the Southcentral coast as it looks to linger over the area going into next week. -BS && .AVIATION... PANC...VFR conditions and light winds will persist. Scattered showers near the terminal this morning and ceilings at times close to MVFR range should lift and scatter out as showers dissipate by later this morning. && $$