626 FXHW60 PHFO 160152 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 352 PM HST Tue Jan 15 2019 .SYNOPSIS... A ridge over the islands will shift southeast ahead of an approaching front. The front will reach Kauai on Thursday and move across Oahu and Maui County Thursday night. The front will stall over the Big Island on Friday. A high will build north of the islands over the weekend. A ridge southwest of the high will shift south over the islands early next week. && .DISCUSSION... A east to west surface ridge lies over Kauai this evening. The ridge will produce light winds and dry weather over the main Hawaiian Islands through tonight. Skies will remain rather cloudy through the morning, but these clouds will produce little rain. The ridge will shift southeast over the next few days ahead of a trough aloft and and associated front approaching from the northwest. Kona winds (winds blowing from the south) will develop tomorrow, then strengthen and shift out of the southwest tomorrow night as the front gets closer. Bands of scattered prefrontal showers may develop over Kauai and Oahu starting tomorrow night. The front will reach Kauai on Thursday and push down to the Big Island on Friday. Winds at the surface will shift rapidly from southwest ahead of the front to north behind the front. There will be widespread showers along the front. The trough aloft will be fairly strong, so the atmosphere will be unstable enough for locally heavy showers and thunderstorms will be possible. The front will be moving fast enough to limit rainfall accumulation. The trough aloft will produce very windy conditions and low temperatures on the summits of Mauna Kea and Mauna Loa. Snow is likely on Friday. The front will stall and weaken near the Big Island starting Friday night. The forecast timing of the front may need to be adjusted. The global models are in pretty good agreement, but differences remain. A new surface high will move eastward behind the front. Surface winds will veer from north to northeast on Friday and to east on Saturday. A ridge trailing southwest from the front will shift towards the islands early next week and winds will shift out of the southeast. && .AVIATION... Ridging over the area will keep the atmosphere dry and stable with VFR conditions prevailing through tonight. Sea breezes over the islands this afternoon will transition to land breezes tonight under a light background wind flow. No AIRMETs are in effect, nor expected through tonight. && .MARINE... A ridge near the islands will produce light to gentle variable winds through tonight. An approaching cold front will shift winds around to the south on Wednesday, with fresh to strong south to southwest winds expected for Thursday ahead of the front. The cold front is expected to sweep eastward through the islands late Thursday through Friday, with fresh to strong north to northeast winds following the frontal passage. Fresh to strong trade winds are expected to fill in late Friday through Saturday as a quick moving high builds eastward to the north of the state. A new approaching cold front will likely shift winds back around to the south and southeast late in the weekend through early next week. A new reinforcing northwest swell is starting to fill in this afternoon and is expected to peak tonight at warning levels. A High Surf Warning (HSW) is in effect through tonight for the building northwest swell across exposed shores of Kauai, Oahu, Molokai and Maui. A High Surf Advisory (HSA) is in effect for west facing shores of the Big Island. Latest buoy readings are indicating the swell is running higher and slightly slower than guidance. This would suggest surf holding at or near warning levels through early Wednesday morning and possibly into the first half of the day Wednesday. Depending on the buoy readings overnight, the HSW may need to be extended or downgraded to an advisory. Starting late Thursday, a new large, short-period, northwest shifting to north swell will build Thursday night and Friday, then slowly fade over the weekend. This swell may reach advisory levels for exposed north and west facing shores Thursday night and Friday. The Small Craft Advisory (SCA) for elevated seas is expected to continue through tonight for portions of the coastal waters exposed to the series of northwest swells moving through. This SCA may need to be extended through Wednesday. Additionally, SCA conditions will likely develop ahead of and behind the cold front across portions of the coastal waters Thursday through Friday. The combination of winds and a large short-period north to northwest swell will create unfavorable boating conditions. Beyond Friday, a period of strong trades may also produce SCA level winds across the typically windy zones around Maui and the Big Island Friday night through Saturday. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Warning until 6 AM Wednesday for north and west facing shores of Niihau, Kauai, Oahu and Molokai and north facing shores of Maui. High Surf Advisory until 6 AM Wednesday for west facing shores of the Big Island of Hawaii. Small Craft Advisory until 6 AM Wednesday for all Hawaiian waters except Maalaea Bay and leeward Maui County waters. && $$ DISCUSSION...Donaldson AVIATION...TS MARINE...Kino