Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
666 FXHW60 PHFO 291401 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 401 AM HST Sun Jun 29 2025 .SYNOPSIS... Trades will ease and veer slightly east southeast into early next week as a broad and weak surface trough sets up over Hawaii. Incoming clouds and showers will focus windward mostly overnight, with localized sea breezes bringing chances for rain leeward today. Trades shift back easterly around Tuesday and continue through the rest of the week. && .DISCUSSION... High pressure far northeast of Hawaii will maintain moderate trade wind flow, however, a broad low level trough over the western end of the state will veer the wind direction at a modified east southeast over the next couple days until the feature weakens and slides westward. Wind direction and speed will be further influenced by local terrain and upstream blockage from the Big Island allowing sea breezes to set up in some areas this afternoon. In addition to the wind shift, instability provided by this weak troughing near the state combined with pockets of moisture moving in on the trades may be enough to enhance the incoming showers. These showers will focus windward and mauka showers during the overnight hours and early morning hours the next couple days, including this morning where radar currently shows scattered showers across the island chain. Clouds and showers are forecast to fill in over island interiors and leeward areas in the this afternoon, and Monday and possibly Tuesday afternoons, where any sea breezes manage to develop in the lighter wind flow. Any significant uptick in shower coverage or intensity will be stifled by a midlevel inversion at around 8000 feet. By midweek, the low level flow will back out of the east and strengthen to moderate to locally breezy levels, with pockets of moisture riding in on the trades. Heading into next weekend, the surface high to our northeast will gradually build, strengthening the local pressure gradient and bringing breezy easterly trades across the island chain. Overall, typical trade wind weather can be expected through the second half of the week with periods of windward and mauka showers. && .AVIATION... AIRMET Sierra posted for tempo mountain obscurations above 2500 feet for windward sides of Kauai, Oahu, Molokai, Maui and Big Island due to abundant incoming low clouds and showers impacting windward slopes of these islands. Expect these showers to decrease through the morning with possibility of scaling back AIRMET Sierra. However, clouds and showers are expected to fill in over leeward and interior sides of the islands due to sea breeze convergence. Brief mountain obscurations will be likely through the day, and will monitor for more extensive coverage in these areas through the day to determine if AIRMET Sierra will need to be issued for leeward areas as well. No other AIRMETs are expected today. && .MARINE... Moderate to locally breezy trades are expected to gradually decrease through Monday as the ridge to our north weakens due to a pair of troughs developing far north and northwest of the state. Early this week, with the pair of aforementioned troughs, trades should veer slightly toward the east-southeast and weaken to gentle to moderate speeds. Moderate to fresh trades could return as early as Tuesday as the troughs move away from the area and a high builds far north of the state. Surf along south facing shores should see a small, long-period south swell slowly fill in today into Monday with surf peaking near or slightly above the summertime average. This swell will then gradually decline through the rest of the week. Surf along east shores will gradually decline over the next several days due to the trade winds weakening. Surf along north facing shores will remain tiny throughout next week. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION/AVIATION...Foster MARINE...Walsh