Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
602 FXHW60 PHFO 310112 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 312 PM HST Sat Aug 30 2025 .SYNOPSIS... Moderate trades continue through next week. Localized sea breezes will favor a brief uptick in afternoon showers Sunday into Monday for some areas. Dry conditions then return Tuesday onward. && .DISCUSSION... Moderate trades foster a hybrid sea breeze pattern this afternoon with onshore flow noted in most leeward and sheltered areas. This has amounted to little more than some enhanced cloud cover in these locales as capping remains strong and mid-level dry air remains entrenched over most of the state. For the Big Island, PWATs have crept toward 1.50" per latest model analysis as the eastern portions of the forecast area are grazed by the northern periphery of an envelope of tropical moisture that is centered to the south. Visible satellite indicates plenty of clouds socked in below the 7.5kft trade wind inversion, and radar indicates offshore showers from this morning have mixed upslope bringing rainfall to interior/upslope portions of the island this afternoon. Conditions clear out in typical fashion this evening. Little change to the synoptic scale pattern for tomorrow and Monday as this envelope of moisture spreads westward across the state. As such, anticipate increased shower activity along sea breeze convergence zones, particularly over the western slopes of the smaller islands on Sunday followed by activity focused mainly over Oahu and Kauai by Monday as moisture begins to exit stage left. Weak cyclonic flow aloft will weaken the inversion slightly over Oahu and Kauai giving showers a boost in intensity, particularly over interior and Leeward Kauai, but organized heavy rainfall is not anticipated. Mugginess will also be on the rise during time as dewpoints creep into the low 70s no later than Monday and persisting into Tuesday. Strong capping then builds in beneath mid-level ridging for the remainder of the forecast period. Meanwhile, seasonably weak ridging at the surface will maintain continued moderate trades. && .AVIATION... Light to moderate trade winds and stable conditions will continue through the weekend. MVFR ceilings and visibility in SHRA will mainly affect windward Big Island and Maui and the Kona slopes of the Big Island tonight as an area of enhanced moisture passes over the southern end of the island chain. AIRMET Sierra for mountain obscuration may be needed on portions of these islands tonight, followed by improving conditions Sunday. VFR should prevail elsewhere. && .MARINE... A ridge of high pressure north of the state will gradually shift further south during the next day or so in response to a developing low far north of the state. As the ridge meanders closer to the islands our trade wind speeds will decrease, with gentle to moderate trades expected through early next week. Winds should be light enough for localized sea breezes, especially across leeward waters. Surf along south facing shores is expected to steadily decline Sunday into Monday as the south swell fades, returning to background levels by early next week along south facing shores. Surf along north facing shores will see a small, short-period swell expected to arrive late this weekend. This swell will be overshadowed by longer period energy out of the northwest starting Monday night. This swell should peak on Tuesday and could produce surf heights near the September average of 4 to 6 feet. Daytime ASCAT showed gale-force winds with the developing low far north of the state. This should send another reinforcing pulse out of the north around the same time the northwest swell arrives. A mix of north and northwest swells are expected next Tuesday through Thursday. Below average surf is expected to continue along east facing shores due to gentle to moderate trade winds persisting through early next week. Peak monthly high tides, combined with water levels running higher than predicted, may lead to minor flooding along the shoreline and in low-lying coastal areas toward the end of next week. Coastal flooding may be possible around the daily afternoon peak tide. && .FIRE WEATHER... Winds remain rather light as moderate trades prevail through the forecast period. Sea level dewpoints creep into the 70s no later than Monday and continue into Tuesday ensuring RH remains elevated during this time. Drier conditions return mid-week onward. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...JVC AVIATION...Wroe MARINE...TS FIRE WEATHER...JVC