Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
769 FXHW60 PHFO 211317 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 317 AM HST Thu Aug 21 2025 .SYNOPSIS... High pressure north of the islands will maintain moderate to locally breezy trade winds through at least the weekend. Typical stable summertime conditions will bring periods of mainly windward and mauka showers, while most leeward areas remain rather dry. && .DISCUSSION... No significant changes to the forecast this morning. Most of the grids were updated to reflect the latest run of the National Blend of Models, with little change to the overall forecast. The main change was a lowering of the PoPs over windward Big Island over the next couple of days. High pressure remains far north and northeast of the islands, driving moderate to locally breezy trades to the region. A mid- level ridge over the islands is maintaining stable conditions, limiting rainfall totals over most areas. A shallow pool of showers and low clouds carried in on the trades brought some showers to windward portions of Maui County and the Big Island overnight. Some of that moisture is expected to reach Oahu later this morning. Satellite shows limited moisture moving in behind this pool of moisture Little change to the typical mid August weather pattern is expected through the weekend, followed by a possible slight decline in winds late Sunday into Tuesday. A persistent mid-level ridge will maintain stability, and little organized moisture is seen in the guidance until Tuesday. As a result, expect limited windward rainfall, and with the exception of the Kona slopes of the Big Island, most leeward areas will remain rather dry. && .AVIATION... High pressure to the northeast of the islands will maintain moderate to locally breezy trade winds over the next couple of days. Clouds and showers will remain focused over the windward and mountain areas, particularly overnight and into the morning hours. MVFR conditions will be possible in showers, otherwise VFR will likely prevail. No AIRMETs are currently in effect. && .MARINE... A high pressure ridge north of the Hawaiian Islands will maintain fresh to locally strong trade winds lasting into early next week. The Small Craft Advisory (SCA) remains in effect for the windier waters and channels near Maui County and the Big Island through Saturday. This SCA will likely continue for these windier waters into early next week. A series of small overlapping medium and long period south (170-190 degree) swells will continue for the rest of this week, with surf heights near the summertime average through Saturday along south facing shores. The largest of these south swells will arrive in the islands later today and hold through Friday. Surf heights should decrease to background levels early next week as the swell energy fades. Another small, long period south swell will arrive by next week Tuesday. Choppy conditions will continue for east facing shores through the forecast period due to the persistent fresh trades. Surf along north facing shores will remain nearly flat through next week. Peak high tides associated with the lunar cycle will lead to minor coastal flooding along shorelines and low lying coastal areas during the high tide later this afternoon. A Coastal Flood Statement remains in effect for minor coastal flooding in low lying areas. && .FIRE WEATHER... Trade winds will remain in the moderate to locally breezy range into Sunday while a ridge aloft maintains an inversion between 5,500 to 7,000 ft. Under this rather typical August weather pattern, afternoon relative humidity should remain near summertime average on Thursday. Slightly drier conditions are possible Friday into the weekend. As a result, near critical fire weather conditions are expected, though we do not anticipate fire weather headlines at this time. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...M Ballard AVIATION...M Ballard MARINE...Bohlin FIRE WEATHER...M Ballard