Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
515 FXHW60 PHFO 130638 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 838 PM HST Mon Oct 12 2026 .SYNOPSIS... Light to moderate trades with local land and sea breezes will become moderate to locally fresh on Tuesday as winds strengthen a little. Trade winds then weaken on Wednesday, followed by restrengthening towards the end of the week into the weekend. Showers overall will be light and focus over windward and mountain areas with light leeward cloud buildups today. More shower coverage is expected tonight through tomorrow morning for the Big Island due to a weak trough transiting then dissipating tomorrow. Drier conditions take hold by mid week followed by slightly wetter trades this weekend. && .SHORT TERM UPDATE... Showers are moving onshore this evening along windward Big Island as the trough moves westward over the island. These showers are anticipated to continue throughout the night. Increased shower chances to near 100% for windward Big Island thoughout the night, and increased QPF as well. Otherwise, the previous forecast remains on track. && .PREV DISCUSSION... Issued at 308 PM HST Mon Oct 12 2026 This afternoon, the Hawaiian Islands are positioned between two weak troughs, one to the northwest, and another to the east. A relatively dry airmass lingers over the region with a stable 5,000 ft inversion in place for the smaller islands. The Big Island today is being influenced by a passing weak trough, with a 12,000 ft inversion and a few heavier showers. This trough is also being supported by a passing mid level low. The showers over windward Big Island should linger tonight into tomorrow morning, then dissipate as the surface trough weakens, and the mid level low drifts east. Showers over leeward Big Island today should dissipate after sunset as daytime heating disappears and typical night time land breezes begin. Some of the moisture associated with the weak trough could spread to the smaller islands, bringing occasionally scattered showers to windward and mountain areas Tuesday. By Wednesday, conditions are forecast to become drier, and winds decrease, bringing only a few pop up clouds to leeward and interior areas. Trade winds then are expected to increase Thursday into the weekend as high pressure to the north becomes established and strengthens. As trade winds increase, passing showers will favor windward and mountain areas, and could increase slightly this weekend. && .AVIATION... Generally light to occasionally moderate trades will persist through the period. Lighter winds may allow localized sea breezes to develop during the daytime hours. Thickening afternoon clouds with scattered showers over windward-facing slopes is possible. MVFR ceilings and visibilities within periods of passing showers over eastern-facing Big Island regions will likely impact HTO. Otherwise, VFR conditions will prevail over most terminals. AIRMET SIERRA is in effect for mountain obscuration along Big Island`s east and southeast-facing slopes until further notice. && .MARINE... Issued at 308 PM HST Mon Oct 12 2026 Gentle to moderate trade winds will gradually increase from east to west through Tuesday as a weak low fills northwest of Kauai and a surface ridge builds north of the state. Moderate to locally fresh trades will strengthen Thursday as surface high pressure builds far north of the state, and a Small Craft Advisory (SCA) will likely be needed for the typically windy waters around Big Island and Maui. Trades will further strengthen Friday into the weekend and may require an expansion of the SCA to additional waters. Small surf will persist along north facing shores into the evening. A fresh, long period northwest swell will build late tonight and Tuesday, pushing surf along north and west facing shores to near seasonal average through Wednesday. This swell will decline Thursday and Friday. A medium period north- northwest swell will build late Friday and will be the main source to produce surf around seasonal average during the weekend, though a small longer period northwest swell will also arrive during the weekend. South shore surf will remain above seasonal average through the afternoon then gradually lower tonight through Wednesday as a long period south-southwest swell slowly declines. Another long period south swell will produce surf near seasonal average Friday and Saturday. Surf along east facing shores will remain small through Thursday as small wind waves and tiny east swell persist. Choppy surf will increase slightly as trade winds strengthen across the region Friday into the weekend. && .FIRE WEATHER... Issued at 308 PM HST Mon Oct 12 2026 Light to moderate trade winds will continue for the first half of the week. Dry air will keep RH levels near- critical values for parts of the state through the week, but winds will be light. Inversion heights range from 5,000 feet toward Lihue to 12,000 feet near Hilo. Winds increase for the second half of the week, but moisture improves marginally. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM UPDATE...Vaughan DISCUSSION...Tsamous AVIATION...Blood MARINE...Wroe FIRE WEATHER....Tsamous