435 FXHW60 PHFO 191944 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 944 AM HST Thu May 19 2022 .SYNOPSIS... Moisture along a weakening front will maintain higher shower chances for Kauai through tomorrow, with flooding rainfall and thunderstorms possible this afternoon. The rest of the state will experience mainly spotty afternoon showers under decreasing southeast to south winds. Layered clouds will gradually diminish today as humid conditions persist through Friday. Moderate trade winds will build during the weekend and will hold into next week. && .DISCUSSION... Humid southerly winds will produce areas of heavy showers today, especially around Kauai, while layered mid to high clouds thin. Active showers persist along a stalled front just northwest of Kauai, though little rainfall is occurring from Oahu to the Big Island this morning. The strong upper level trough that brought stratiform rainfall to mainly Kauai and Oahu yesterday is pushing east of the state this morning. Mid to high clouds will slowly thin, but conditions will remain somewhat unstable as the upper trough slowly departs. As a result, expect low clouds and spotty heavy showers to develop over the islands this afternoon, especially around Kauai where a Flash Flood Watch remains in effect due to the proximity of the lingering deep moisture. There could be areas of gusty south winds to the north of terrain on Kauai and Oahu today, but as winds decline this afternoon, sea breezes should dominate over most areas. With dew points hovering in the lower 70s, humidity will remain high. Tonight and Friday, a humid land and sea breeze regime will prevail from Oahu to the Big Island, while a band of moisture along the dissipated front stalls over Kauai. Upper level ridging will be slowly building, but a lingering mid level trough will maintain some instability. As a result, expect clouds and spotty showers, some briefly heavy, to develop over most islands in the afternoon and diminish during the overnight hours. Cloud cover and shower chances will remain highest over Kauai. There does not appear to much of a flood threat on Kauai tonight and Friday morning, but heavier rainfall possible Friday afternoon could lead to short term flooding concerns. An increasingly stable trade wind flow will build during the weekend. High pressure far northeast of the state will strengthen, causing trade winds to slowly increase and push the deeper moisture west of the state. A mid level ridge will also build overhead and bring increased stability. The result will be a return to typical trade wind weather that will hold into next week. && .AVIATION... A broad field of gentle background ascent within the established moist southerly flow regime will result in periodic low clouds and showers focusing over leeward zones. A few showers may be locally heavy, mainly near Kauai which is located within the eastern edge of the deepest moisture. Likewise, Kauai will experience a greater frequency of MVFR through the forecast period. Showers will further increase over Kauai tonight as a remnant front approaches from the west. AIRMET Sierra for mountain obscuration is in effect for Kauai & Lanai, and will likely remain in effect for Kauai through tonight. Light icing is possible within the 14.5-25kft mid/upper cloud layer. && .MARINE... Strong southerly winds will continue over Kauai waters today as a slow moving cold front stalls just west of Kauai. The southerly winds and a long period south swell are producing rough seas over southern leeward waters near Kauai and Niihau that are normally protected during a typical trade wind weather pattern. A Small Craft Advisory (SCA) remains in effect for all waters around Kauai through this afternoon. Expect locally higher winds and seas near heavy showers and thunderstorms. The front is expected to weaken as it lifts northward later this evening with a sharp drop in southerly winds by tonight. High pressure will begin to build back over the region Friday with easterly trade winds strengthening from east to west across the area this weekend. SCA conditions will likely return to the typical windier waters and channels around Maui County and the Big Island as this happens. Surf heights along south facing shores will remain elevated into the weekend as the current south swell becomes reinforced today. In the long range, models show quite a bit of activity in the southern hemisphere, which could translate to a few south shore surf events over the next week or so. Surf along north and west facing shores will trend up today as a small, medium-period northwest (300-320 degrees) swell arrives. A return to small, summer-like conditions is expected over the weekend and into the first half of next week as this swell energy fades. && .HFO WATCHES/WARNINGS/ADVISORIES... Flood Watch until 6 PM HST this evening for Niihau-Kauai- Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters- Kauai Channel. && $$ DISCUSSION...Wroe AVIATION...JVC MARINE...TS