588 FXAK68 PAFC 020034 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 434 PM AKDT Fri Sep 1 2023 .ANALYSIS AND UPPER LEVELS... Weak ridging moves over the eastern Bering Sea and portions of Southwest Alaska tonight and will shift into Southcentral through tomorrow. Behind it, upper level long wave troughing moves into the western Bering Sea, with an associated surface level low developing in eastern Russia and tracking towards the Norton Sound. The front extending off the low tracks across the Bering and Aleutian Chain towards the Southwest coast through Saturday night pushing and pushing inland early Sunday morning. && .MODEL DISCUSSION... Models remain in good overall agreement through mid next week. There are some model differences with a low moving out of eastern Russia towards the western Bering Sea towards the end of next week. && .AVIATION... PANC...Gusty southerly winds will diminish through the evening and overnight hours. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Tonight through Monday)... Gusty southwesterly winds continue across the region as a broad North Pacific ridge drives winds toward low pressure over Interior Alaska. These winds are additionally bolstered by a strong upper trough passing to the north this evening. As the trough pushes east tonight, winds will shift out of the west, weakening the up-Inlet flow. As a result, winds relax tonight for Anchorage and the Mat-Su Valleys, and they also diminish somewhat along the western Kenai. Cooler, drier air works in behind the trough axis. Combined with weak low pressure developing in the northern Gulf of Alaska, this will produce offshore gap flow, with the strongest focus through Passage Canal, where winds are expected to gust to 35 mph near Whittier. Upslope rain showers will continue this evening along the western slopes of the Talkeetna and Wrangell Mountains, as well as within Eastern Prince William Sound. Glennallen is likely to see a period of rainfall with this system this evening. With the upper trough pushing east tonight, rainfall will diminish from west to east overnight, leading to a fairly dry Saturday across Southcentral. Offshore gap winds will diminish in kind. Late Saturday night into Sunday morning another system approaches from the west. A band of upslope precipitation is likely to set up on the front range of the Chugach and the Talkeetna Mountains, south across the Kenai Peninsula as a warm front pushes into Southcentral Alaska. There may be a period where precipitation decreases Sunday morning as the warm front continues eastward. A second round of precipitation arrives with the cold front later on Sunday. Southerly gap winds are expected to develop briefly as the low moves in over the Interior. These winds diminish Sunday night as the low pressure in the Interior weakens somewhat, and a triple point low develops in the northern Gulf, nullifying much of the pressure gradient along the coast. The lows exit east for Monday as a strong, but transient ridge builds in, leading to more benign weather to start off the work week. && .SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days 1 through 3: Tonight through Monday)... Rain showers are ongoing across Southwest tonight and will only increase in intensity as multiple waves of energy track across the region. A front with a decent amount of moisture will make its way into the western Bering/ Aleutians tonight and begin its track eastward towards Southwest. Meanwhile, persistent west- southwesterly flow coinciding with high tide and higher seas could raise water levels 1 to 2 feet above normal highest tide, especially between Newtok and Kipnuk tonight. However,the threat for elevated water levels across the Kuskokwim Delta coastline will continue through Saturday night as the aforementioned front impacts Southwest. With higher sustained winds and gusts reaching 35 to 45 mph across the Kuskokwim Delta coast Saturday afternoon through Saturday night, this raises the concern for elevated water levels for the Kuskokwim Delta. The resulting higher seas and surf coinciding with high tide could raise water levels 2 to 4 feet above normal highest tide, especially between Newtok and Kipnuk Saturday into Saturday night. As a result, a Special Weather Statement has been issued for tonight into Saturday night. Total rain accumulations with this frontal passage across Southwest will range from 0.5 inches to 1 inch of rain. Highest amounts will be along the mountain ranges and across the Kuskokwim Delta. As we head into the beginning of the work week, chances for rain will decrease and winds will relax. Out west, the aforementioned front will track into the western Bering tonight and will have a swath of gale force winds from Saint Matthew Island to Adak by Saturday afternoon. Due to the favorable orientation of west-southwest through Dutch Harbor, some funneling and enhancement of the winds are likely. Peak winds of 35 knots gusting to 45 knots are forecast with higher gusts possible before midnight. Saturday night into Sunday, the front will reach the eastern Bering/Aleutians and its winds will begin to weaken. As we head into the beginning of the work week, a ridge will build behind the frontal passage and result in calmer conditions across the Bering, with the exception of areas of small craft winds on either side of the ridge. &&.LONG TERM FORECAST (Days 4 through 7)... An active pattern looks to continue through the extended period. The late weekend system looks to clear from Southwest Alaska late Sunday night into Monday morning and then start clearing from Southcentral Monday night. Ridging will build in behind the aforementioned system, but the pattern will remain progressive enough that the next system will start approaching western Alaska by Monday afternoon/evening. Models are in good agreement in placement and timing of this low as it approaches the coast, but much greater disagreement as models track this system inland. However, general consensus has the trough elongating with a new low developing on the southern end near Cook Inlet and the Kenai Peninsula towards midweek. This solution would allow for widespread light to moderate rainfall chances across much of Southwest Alaska and spreading inland across the Alaska Range, Talkeetna Mountains, and Mat-Su Valley. This solution would also enhance precipitation along over the Prince William Sound and Southcentral Coast with lesser precipitation chances for areas further inland. && $$ SYNOPSIS AND MODEL DISCUSSION...KM SOUTHCENTRAL ALASKA...CQ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...NS LONG TERM...PP