000 FXHW60 PHFO 281343 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 343 AM HST Tue Jun 28 2022 .SYNOPSIS... A strengthening high pressure system far north of the Hawaiian islands will keep moderate to breezy trade winds blowing across the state through the weekend. Passing clouds and showers will drift through windward and mountain areas, favoring the overnight to early morning hours. An upper level disturbance may briefly increase cloud and shower coverage this weekend. && .DISCUSSION... This mornings satellite picture shows fairly stable clouds riding in on the trade winds into windward and mountain areas of each island. A weak subtropical jet stream continues to produce scattered high level cirrus clouds over the islands enhancing sunrise and sunset colors. Local radar imagery continues to show isolated to scattered light showers developing across the state. Upper air balloon soundings from 12Z (2 AM HST) this morning show trade wind temperature inversion heights at 6,700 feet at Lihue and 6,000 feet at Hilo. These inversion heights typically lead to more stable scattered light shower activity, which matches well with the early morning radar and satellite imagery. In the big picture, a strengthening surface high pressure system roughly 1,400 miles north of the islands will continue to produce moderate to breezy trade winds across the region through the weekend. Model cross sections continue to show subsidence temperature inversion heights in the 6,000 to 8,000 foot range, allowing clouds to grow taller, and produce passing showers over windward and mountain areas through the week. In the longer range forecast for the weekend, an upper level low continues to track from southeast to northwest across the region. Rainfall impacts with this system will depend heavily upon how close this low center tracks relative to each island and are highly variable this far out in the 5 to 7 day forecast time period. Stay tuned. No significant changes to the forecast grids this morning as guidance remains on track for the next seven days. && .AVIATION... Moderate to locally breezy trade winds are expected to persist through twenty-four hours and beyond. Bands of weak trade wind showers will impact mainly windward slopes and coasts. Isolated MVFR CIG and VIS are to be expected in passing showers. Otherwise, VFR conditions will prevail statewide. Regarding Leeward Big Island, a weak eddy remains anchored just west of the island. This has kept a broad area of VFR cloudiness across the Kona coast overnight. Clouds are expected to lift in the afternoon, but may spread further inland in the afternoon due to weak sea breezes. AIRMET Tango is in effect for low-level mechanical turbulence below 9000 feet over and downwind of island terrain. Conditions are likely to persist through at least early evening. && .MARINE... Fresh to strong easterly trade winds have returned and are here to stay through the upcoming weekend as the ridge strengthens to the north. Trades may become strong over most waters Friday through the weekend as 1030-1035 mb high sets up due north of the islands. Seas will respond and become rough, potentially reaching the 10 ft Small Craft level over the waters south of the Big Island and in the Alenuihaha Channel this weekend. Surf along south facing shores will hold this morning, then trend up slightly this afternoon as a fresh south swell arrives. Heights will near the 10 ft (faces) advisory level by tonight and another advisory can't be ruled out later today if observations come in higher than predicted. Buoy observations to the south reflect a slight upward trend in the 15 sec band this morning, which supports the surf trending back up through the day. This new pulse should peak this evening through Wednesday, then ease through the second half of the week. Surf along east facing shores will steadily trend up through the week as the local and upstream trades increase. This should result in rough conditions for easterly exposures by and through the weekend. Confidence remains low for any long-period pulse locally associated with Tropical Storm Celia in the far eastern Pacific. Surf along north facing shores will remain at seasonal levels (near flat) through the week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Bohlin AVIATION...Bedal MARINE...Gibbs