Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
030 FXHW60 PHFO 291335 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 335 AM HST Fri Aug 29 2025 .SYNOPSIS... Dry and stable weather will prevail across the islands the next several days with light to occasionally moderate gust trade winds. Other than a higher surge of moisture skirting Big Island and Maui County and increasing rain chances early next week, the majority of light precipitation will fall along the Kona slopes of Big Island in relation to the sea breeze and within higher upslope windward mauka terrain. && .DISCUSSION... An slightly stronger than normal upper to mid level ridge is anchored atop the state and this will result in very stable conditions going into the weekend. A trough extending from a deepening low north of 40N has continue to support a slackened pressure gradient back toward the islands from a surface high centered 1,200 miles from Hilo, Hawaii. Early morning shortwave IR satellite showing many pockets of incoming low-topped warm clouds trapped within moderate oceanic trade flow. Radars remain fairly quiet this morning with only light showers forming within downstream island plumes. Morning soundings depicting continued below normal precipitable waters of around 1.2 to 1.3 inches. A relatively shallow boundary layer with a 7-8k foot inversion height guarantees minimal areal shower coverage. Any light precipitation that does fall will remain focused along windward upslope mauka or leeward afternoon sea breeze boundaries that interact with trade flow riding overtop ridge tops or channeling through valleys. Most areas that pick up measurable rain will likely only receive a few hundredths to a tenth of an inch, at most. As was the case yesterday, a few spots may pick up a quick quarter of an inch or slightly more within these weaker trades along the slopes of Mauka Kea and Mauna Loa as well as Kauai`s Mount Waialeale. Light to moderate trade winds, along with this stable and dry weather pattern, will persist over most of the state through the entire 7 day period. The only caveat will come Sunday and Monday as model guidance is showing a slug of deeper, more rich tropical moisture moving up from the ITCZ and grazing Big Island. If this does occur, the likely result would be enhanced shower activity along the Kona and Kau slopes Sunday afternoon into evening. A compact upper level low meandering northwest of Kauai early next week could lead to more shower activity in or around the Garden Island. && .AVIATION... Light to moderate trade winds with localized daytime sea breezes and nocturnal offshore land breezes. Thicker clouds and showers will mainly focused over more windward exposures and mountainous regions. A few brief afternoon leeward showers are possible along the sea breeze boundary. Overall, VFR conditions will prevail with MVFR conditions occurring within heavier showers. No AIRMETs are in effect and none are expected. && .MARINE... A developing low far north of the islands has displaced the typical high pressure ridge north of the islands, thus keeping gentle to locally fresh trade winds through early next week. Observations at nearshore PacIOOS buoys south of the islands show that the long period forerunners have filled in overnight. Surf along south facing shores will peak through the day near summer averages before declining slowly over the weekend. Surf heights will return 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 generated by a storm force low developing near Kamchatka that will arrive around the first half of next week. This swell could produce surf along north facing shores near the September average of 4 to 6 feet during its peak. Below average surf 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 that are 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 peak tide, which will be during the afternoon hours. && .FIRE WEATHER... Weaker trade winds will stay well below critical fire weather thresholds within areas that fall below 50% RH during peak afternoon warmth. High stability and dry conditions are expected to remain the main theme well into next week. Inversion heights will typically range between 6k to 8k feet. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Blood AVIATION...Blood MARINE...Shigesato FIRE WEATHER...Blood