FXHW60 PHFO 250636 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 836 PM HST Sat Jul 24 2021 .SYNOPSIS... Moderate to breezy trade winds will remain through next week. Showers will continue to ride in on the trades, with an increase in rainfall and humidity likely Sunday afternoon into Tuesday. Brief downpours are expected during this time especially across windward and mountain areas. && .DISCUSSION... Persistent high pressure north of the main Hawaiian islands keeps the pressure gradient steep enough to support moderate to breezy trade winds across local waters this evening. Clouds and showers continue to favor windward and mauka areas, representing a weather pattern expected to remain in place through the forecast period. Expect remnant moisture associated with former Tropical Cyclone Guillermo to move through the state Sunday. Heavier showers will affect windward and mountain areas as well as Kona slopes of the Big Island starting Sunday afternoon. Increased moisture will spread to rest of the island chain by Monday. The greatest rainfall will likely occur over the Big Island and windward Maui from Sunday afternoon through Monday. By Tuesday afternoon, a drier airmass will begin to move into the eastern half of the state, while moisture continues to linger over the far western end of the state. By Thursday we should see this increased moisture move off to our west as drier trade wind weather returns across the state from the east. && .AVIATION... Similar to the last few nights, moderate to occasionally breezy east northeasterly trades will act to concentrate most scattered shower activity along the windward coasts and slopes. Periods of MVFR ceilings and visibility may accompany this activity. Isolated showers over leeward sides, but expect mainly VFR conditions. AIRMET TANGO remains in effect for areas below 9000 feet over and immediately south thru west of mountains due to tempo moderate turbulence. AIRMET SIERRA remains in effect for north thru east sections of Kauai, Oahu, and the Big Island above 2000 feet for mountain obscuration from clouds and showers. && .MARINE... Surface high pressure far northeast of the state will maintain locally strong trade winds through Monday. Also, expect slightly elevated, rough seas over waters exposed to these gusty trade winds. A Small Craft Advisory (SCA) remains in effect for the typically windier waters adjacent to the islands of Maui County and the Big Island through Monday afternoon. The SCA may need to be extended through Monday night for these same waters, but there may be a slight weakening of the trades from Tuesday into mid- week. The trade winds will produce slightly elevated, choppy surf along east facing shores through early Sunday. The guidance indicates the trade wind swell will likely trend lower early next week as the trades weaken in the vicinity of the islands, as well as upstream of the state. A small south swell will continue to generate surf heights near the summer-time average along south facing shores through early Sunday. As the small south swell declines, expect surf heights to trend lower along south facing shores during the day on Sunday. From Monday through mid-week, short- to medium-period southeast trade wind swell energy originating from the Southern Hemisphere will keep small surf along exposed shorelines, such as south facing shores of Kauai and the Big Island, as well as select locations along the south shore of Oahu. Surf will remain nearly flat along most north and west facing shores through the middle of next week. A small west-northwest swell produced by Northwest Pacific Tropical Cyclones may arrive along some exposed west and north facing shores late next week. However, confidence remains low about this at this time. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Monday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Powell AVIATION...JT MARINE...Houston