690 FXHW60 PHFO 051354 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 354 AM HST Sun May 5 2019 .SYNOPSIS... The cold front that quickly moved down the island chain Saturday is slowly moving over the Big Island early this morning. This boundary combined with a secondary band of showers quickly advancing down the island chain will keep the rain chances up across the eastern half of the state today. Some showers may be heavy at times with gusty winds due to a combination of the front and an upper low approaching from the north. Drier and cooler air along with gusty northwest winds will fill in today from west to east, with trade winds unlikely to make a return until later this week. && .DISCUSSION... Early morning observations, satellite data and radar trends showed the front that quickly moved through the islands Saturday now over the Big Island slowly shifting eastward. A secondary band of showers associated with a post-frontal trough is quickly moving through from west to east approaching Maui County. These surface features combined with an anomalously deep upper low dropping south into the area will keep the rain chances up across the eastern half of the state today. Some showers will be heavy at times and capable of producing gusty winds up to 45 mph. Guidance continues to depict the upper low stalling just north of the islands today, then drifting east-southeastward through tonight. Although a storm or two can't be ruled out over the northern Maui County and Big Island windward waters, the better dynamics and forcing for ascent will remain positioned just north of these waters today. Much drier and unseasonably cooler air with gusty northwest winds will fill in from west to east today through tonight as the front continues eastward. Temperatures will only manage to hit the mid- to-upper 70s through the afternoon hours today, then dip into the low-to-mid 60s tonight into Monday morning for the overnight lows. Dewpoints are forecast to drop into the 50s through this time due to the drier air. As the upper level low fills and lifts off to the northeast through the first half of the week, it will leave a weak trough of low pressure over and around the state. Light and variable winds will be the result each day from late tonight through Wednesday, which will give way to a land and sea breeze regime. A return of light to moderate trades will become a possibility through the second half of the week. && .AVIATION... A late season cold front passing over the Big Island will continue to press se at close to 20 kt. Locally strong south to southwest winds are expected along and ahead of the front. AIRMET Tango is currently in effect for low level turbulence across Maui and the Big Island downwind of higher terrain or east of the terrain. Low ceilings and locally heavy downpours along the front have necessitated AIRMET Sierra for mountain obscuration across Northwest Big Island. Conditions are expected to improve by mid morning. Gusty north to northwest winds are expected to develop across the smaller islands this morning and the Big Island this afternoon once the front pushes off to the east. An AIRMET for low level turbulence to the south and east of higher terrain of the smaller islands may become necessary later this morning. && .MARINE... A cold front in the vicinity of the Big Island early this morning, will shift eastward, exiting to the east of the coastal waters by this evening. Strong and gusty west-southwest winds are expected in advance of the front, with strong and gusty west-northwest winds expected behind the front. As a result, a Small Craft Advisory (SCA) remains in effect for the entire marine area through through 6 PM this evening. Winds are expected to trend downward fairly rapidly from northwest to southeast down the island chain tonight and Monday as an area of low pressure north of the islands weakens. This area of low pressure will continue to weaken into a surface trough by the middle of the week, then shift west of the coastal waters on Thursday. As a result, light and variable winds are expected across the marine area Monday night through Wednesday, with overnight land breezes and daytime sea breezes expected near the coast. Light trade winds should begin to fill back in on Thursday, with light to moderate trades then holding in place through next weekend. Winds and seas are expected to remain below SCA levels tonight through next weekend. A moderate-sized, rough and short-period northwest swell will continue to affect the island chain today through Monday, with surf expected to remain below advisory levels as the swell peaks late this afternoon or this evening. Otherwise, a few small swells will maintain small surf along north, west, and south shores through mid-week. A more significant south swell is possible by the end of the week, which could push south shore surf up to near advisory levels. See the Oahu Surf Discussion (SRDHFO) for details on the swell sources. && .HFO WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 6 PM HST this evening for Big Island Summits. Wind Advisory until 6 PM HST this evening for Haleakala Summit. Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters- && $$ DISCUSSION...Gibbs AVIATION...Bedal MARINE...Jelsema