Area Forecast Discussion
Issued by NWS Anchorage, AK
Issued by NWS Anchorage, AK
659 FXAK68 PAFC 120030 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 430 PM AKDT Tue Jun 11 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... A large upper level low and associated surface low remain south of Kodiak Island this afternoon, with a weak flattened ridge over mainland Alaska. Multiple easterly shortwaves between these two features continues to be the main driving factor in precipitation across Southcentral Alaska. Steady showers across the Mat-Su Valley, with lighter precipitation in Anchorage Bowl, will quickly push through the area and end by early tonight. With another approaching shortwave, widespread rain showers will fill in across the Copper River Basin Wednesday morning, spreading westward into the Mat-Su Valley and Anchorage by late afternoon. A few pop-up rain showers are also possible across the western Kenai Peninsula. On Thursday, much of the western Kenai northward through Anchorage and the MatSu Valley will remain dry, but another shortwave descending from interior Alaska will continue scattered rain showers across the Copper River Basin. A few isolated thunderstorms are also possible across the northern portions of the Basin in the late afternoon/evening, however, instability is very marginal. With more instability on Friday, the potential for widely scattered thunderstorms exists for the entire Copper River Basin and possibly in the Susitna Valley as well. High temperatures on Wednesday will be in the 50s for most, with upper 50s to lower 60s on Thursday. Friday will mark the beginning of a warmer and generally drier period, albeit with thunderstorm potential, for Southcentral Alaska with high temperatures in the mid 60s near the immediate coast to mid 70s inland. -ME && .SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3)... Light winds persist across Bristol Bay as the pressure gradient across Southwest Alaska weakens. Broad low pressures sits south of the Alaska Peninsula, cycling weak shortwaves over Southwest and south towards the Eastern Aleutians. Conditions will be mostly dry, however, there will be light rain today as an easterly wave pushes across the region tonight into Wednesday morning. A chance for some wet thunderstorms in western Bristol Bay and along the Western Alaska Range will be embedded in the wave that traverses the Bristol Bay and the Lower Kuskokwim Valley. High pressure builds in the over the western Bering Sea and will progress eastward over the next several days. A low developing west of the Western Aleutians will push south of the Aleutian Chain mid-to- late week, eventually stalling in the North Pacific south of Adak. This will bring rounds of rain showers and small craft winds to the Western/Central Aleutians Wednesday through the end of the week. In Southwest, a benign pattern will set-up by Wednesday evening, with a break in active weather expected until the end of the week. Through Thursday into Friday, northerly flow will drive drier air down from the north into Southwest. && .LONG TERM FORECAST (Days 4 through 7) Saturday through Tuesday... High pressure looks to persist across the eastern Bering, the Alaska Peninsula, and western mainland through most of the long- term period. However, as with cases in the past, the GFS wants to break the ridge down too quick on Sunday while the other guidance has the ridge persisting. Therefore, the GFS seems to be an outlier at this point. Additionally, the ensembles of the GFS also have a similar solution to the deterministic GFS while the ensembles of the other deterministic guidance do indeed have the ridge persisting. All-in-all, odds favor warmer and drier weather over southwest through the long-term with the occasional easterly wave moving through to help induce diurnal scattered showers. Odds favor cooler and unsettled weather over most of the Aleutian Chain with low pressure dominating in the North Pacific. The high pressure over the western mainland looks to nudge eastward through Sunday and provide mostly dry and warm weather to Southcentral for that time. Diurnal showers will be possible for the interior locations of Southcentral and perhaps even thunderstorms if enough instability builds with day-time heating. Confidence then decreases dramatically for the Sunday night through Tuesday timeframe as guidance has different solutions on the orientation of the ridge and how fast or slow the ridge might break down. Thus, forecast uncertainty remains on the high side for Southcentral during the second half of the long-term. && .AVIATION... PANC...Light rain will continue through the evening hours. Light northerly winds will gradually weaken late this evening, being replaced by general up-inlet southerly flow. Rain chances increase again on Wednesday, as well as a chance for MVFR CIGs. && $$