484 FXHW60 PHFO 170153 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 353 PM HST Thu Jul 16 2020 .SYNOPSIS... Lighter winds combined with increasing moisture will translate to warm and humid conditions with increasing showers through Friday. Breezy trade winds will return over the weekend with another batch of showers forecasted to move through Saturday night and Sunday. && .DISCUSSION... A disturbance in the ridge to the north has allowed the trade winds to drop into the gentle trade range today with some afternoon leeward sea breezes. The afternoon visible satellite imagery shows high clouds streaming over the Big Island and northwest of Kauai and scattered low clouds moving westward, upstream of the islands. Satellite precipitable water estimates show an uptick in moisture about 150 miles east of the islands, and this moisture is expected to reach windward areas tonight. That enhanced moisture is associated with a surface trough currently about 500 miles NE of Hilo and is expected to pass north of the islands. Friday, this feature will cut off the trade winds entirely and light and variable winds with afternoon sea breezes will prevail. The trough will bring increasing humidity and showers into the area. With the light winds, clouds and showers will increase in the afternoon and be most prevalent over the higher elevation areas with some rainfall drifting toward the shorelines. The trough is forecast to exit the area by Saturday, allowing the winds to ramp up to breezy levels over the weekend and remain into next week. A drier period is expected Saturday with increasing showers possible Saturday night and Sunday as another area of enhanced moisture moves through with the stronger trades. The aforementioned high, thin cirrus clouds will linger in our area over the next few days providing potential for colorful sunrise and sunset views depending on location and low cloud coverage. && .AVIATION... An area of high pressure to the north of the region will help maintain moderate easterly flow through the rest of this afternoon and into the evening. Tonight, expect scattered showers to mainly affect windward areas and bring brief periods of MVFR ceilings and visibility. Isolated showers elsewhere. No AIRMETs are currently in effect. && .MARINE... A weak surface trough around 500nm east-northeast of Hilo will move westward over the next few days, disrupting the pressure gradient across the islands. This will cause the trade winds to weaken during the next day or so, with local sea/land breezes developing over some leeward nearshore waters through Friday. By this weekend, the surface trough is expected to dissipate as it moves northwest of the islands, while surface high pressure builds far north-northeast of the state. This will allow the trade winds to gradually strengthen this weekend, with Small Craft Advisory conditions potentially developing over the typically windier waters adjacent to the islands of Maui County and the Big Island starting Saturday night, and persisting into early next week. No significant swells are expected into the middle of next week. South shore surf will remain small through Friday, before a small, long-period, south-southwest swell arrives, which may cause a slight bump in surf heights along south facing shores this weekend. The weakening trade winds will cause surf to decline along east facing shores through Friday, then increase again this weekend as the trades re-strengthen. Surf along north facing shores will remain nearly flat for the foreseeable future. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Morrison AVIATION...Thomas MARINE...TS