884 FXHW60 PHFO 150641 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 841 PM HST Wed Aug 14 2019 .SYNOPSIS... Trade winds are increasing tonight with moderate trades in the forecast through Friday. On Saturday, the high pressure ridge north of the state weakens, and light to moderate trade winds return. Isolated to scattered showers remain in the forecast favoring windward and mountain areas through the weekend. Sea breezes will develop along sheltered west facing slopes of all islands through the first half of next week. Higher humidity levels may return by next Tuesday as deeper moisture moves up from the tropics increasing shower activity over the island chain. && .DISCUSSION... A high pressure ridge north of the islands will increase slightly resulting in a slight increase in the trade wind strength through Friday. An upper level trough northwest of the islands continues to produce some high cirrus clouds over the state. A weak low level trough moving through the central islands tonight may produce brief periods of showers mainly along the windward slopes of Oahu and Kauai through the early morning hours on Thursday. Convergence plumes of clouds and showers are seen on evening radar imagery streaming off of the higher mountains of each island. A few showers may move into the leeward areas on Oahu just in time for the Thursday morning commute. Another weak low level trough moves through the islands Thursday night into Friday morning with additional shower activity for windward slopes. Otherwise a fairly dry weather pattern will remain in place through the weekend under a stable high pressure ridge aloft. The high pressure ridge to the north of the state weakens on Saturday producing a downward trend in wind speeds into the light to moderate range lasting through Monday. Isolated to scattered shower activity will favor windward and mauka areas, especially in the overnight to early morning hours. Long range models continue to show a weak disturbance in the tropics bringing up deeper moisture over the islands on Tuesday. Hot and humid weather conditions are likely with enhanced showers spreading from east to west across the state as the system moves down the island chain. Deeper moisture trends with showers associated with this system should last from next Tuesday through next week Thursday. Forecast models are in good agreement with this system and confidence in enhanced showers for next week remains in the fair category this far out. Additional details on this changing weather pattern will be provided this weekend as the intensity and track of this approaching disturbance evolves over time. && .AVIATION... Mostly dry trade wind pattern will continue through the period with VFR conditions prevailing. Clouds and showers will favor windward and mountain locations, which could lead to brief periods of MVFR CIGS and VSBYS. Clouds and showers that developed over leeward areas earlier today due to localized sea breezes will clear overnight and likely reform tomorrow afternoon. No AIRMETs are currently in effect. && .MARINE... A ridge of high pressure, located some 380 miles north of Kauai will continue to move north for the next 24 hours before becoming stationary. This will allow stronger trades to spread across the islands through Thursday, favoring the near-shore waters of Maui County and the waters south of the Big Island. A Small Craft Advisory (SCA) slated to become effective at 6 am HST Thursday, will instead become effective at 10 pm HST tonight for those waters. The SCA is good to until 6 pm HST Friday, as the ridge is expected to weaken over the weekend. A series of small southerly swells produced by storms in the South Pacific can be expected through the remainder of the week and on through the weekend. Brief periods of moderate size surf can be expected during the peaks of these swells. A larger south swell is expected to arrive on Monday, peak on Tuesday, then lower gradually on Wednesday. Surf heights may reach High Surf Advisory levels during the peak of this swell. The current west swell is likely peak overnight tonight, then lower gradually through the remainder of the week and through the weekend. Surf heights will be largest over shorelines with westerly exposure. Strengthening trade winds will cause an uptick in short period choppy surf along east facing shorelines Thursday through Saturday. Diminishing winds over the weekend and early next week will result in lowering surf heights. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Bohlin AVIATION...Powell MARINE...Lau