026 FXHW60 PHFO 310155 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 355 PM HST Wed Oct 30 2019 .SYNOPSIS... Daytime sea breezes and nighttime land breezes will continue through the weekend. An upper trough passing north of the islands will bring the potential for some heavier showers and thunderstorms into this evening and possibly again tomorrow afternoon. Drier and more stable conditions are expected Friday through the weekend. A weak cold front will reach Kauai Sunday into Monday and dissipate. && .DISCUSSION... Water vapor imagery shows an upper low 100 miles north of Honolulu moving towards the east southeast at 20 mph. The upper trough is inducing an area of low pressure at the surface around the islands which is keeping the background wind flow light and variable this afternoon. Visible satellite and radar show partly sunny skies over the islands this afternoon with scattered showers impacting all of the islands to some extent. Some of the showers have been heavy with accumulations near 3 inches on Kauai and 1 inch on Oahu since noon over the windward sections of both islands. The instability provided by the low and moisture available will keep the possibility of heavy showers and thunderstorms through early evening. Land breezes will clear out the islands later tonight with sunny conditions expected in the morning. As the low tracks east tonight, a second upper low will form on the backside of the departing low and move over the western end of the state before tracking eastward through the day Thursday. This could destabilize the atmosphere enough to bring another round of heavy showers and a slight chance of thunderstorms mainly during the afternoon and evening hours in conjunction with the sea breeze. Thursday's chance for heavy rain/thunderstorms will be a bit more limited as the much of the moisture over us today is expected to move east into a more organized convergence band that is not expected to impact the state. Friday and Saturday, the potential for heavy showers is expected to diminish as an upper level ridging builds in. Background winds will remain gentle, but begin to push out of the southwest as a weak cold front approaches from the northwest. Daytime sea breezes and nighttime land breezes will continue to dominate resulting in afternoon clouds and spotty showers followed by clearing at night. The front is expected to stall near Kauai Sunday night and dissipate Monday. A longwave trough will approach the islands towards the middle of next week build another surface trough over the area. Hard to say this far out how much impact will be felt across Hawaii, but it doesn't bode well for a return of the trade winds. && .AVIATION... A low pressure system continues to reside north of the state this afternoon. This feature should help maintain the chance of scattered SHRA/+SHRA well into the evening. MVFR ceilings and visibility will occur where the heavier showers pass over, generally on the windward sides of the islands. By tonight, with the loss of diurnal heating, precipitation and cloud cover are expected decrease in coverage. A sea breeze/land breeze regime will exist across the area tonight and again on Thursday with a light flow pattern in place. No AIRMETs are currently in effect. && .MARINE... An area of low pressure will linger north of the islands during the next couple of days, leading to gentle variable winds over coastal waters and periods of thunderstorms. For the most part, thunderstorms have been passing just north of the coastal waters today, though we could see a few flare near the islands into early evening and again on Thursday afternoon as an upper level disturbance passes overhead. The area of low pressure will lift north of the offshore waters by Friday, eliminating the threat of thunderstorms and keeping winds across the region rather weak. Gentle to locally moderate south to southwest winds will develop late Friday and Saturday as a front approaches. The weakening front may reach Kauai on Sunday. The current north-northwest swell continues to be slow to decline and elevated a couple feet above Wavewatch guidance. The Waimea Bay and Pauwela PacIOOS buoys have been measuring the swell around 7 to 8 ft at 13 to 14 seconds this afternoon, which again warrants the extension of the High Surf Advisory (HSA) for north facing shores from Kauai to Maui through tonight. With the swell shifting out of the north-northwest, surf has dropped along west facing shores, where the HSA has been cancelled. In addition, the Small Craft Advisory for hazardous seas has been dropped. The northwest swell will continue to slowly subside tonight into Saturday, and a HSA will likely be needed again Sunday night and Monday as a another northwest swell passes through. Modest increases in surf are due along east and south facing shores over the next few days. A small short-period northeast swell will persist into Friday, though surf will remain below the advisory level. A small bump out of the south-southwest is expected into the weekend along south facing shores. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory until 6 AM HST Thursday for north facing shores of Niihau, Kauai, Oahu, Molokai and Maui. && $$ DISCUSSION...Foster AVIATION...Thomas MARINE...Wroe