Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
713 FXHW60 PHFO 271959 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 959 AM HST Sat Apr 27 2024 .SYNOPSIS... A plume of moisture moving through the state today will produce passing showers across the state with afternoon showers expected over select leeward areas. A drier weather pattern is expected Sunday into early next week with light to moderate east to east- southeast winds. Winds should be light enough for sea breezes to develop during the day and land breezes at night, especially early next week. && .DISCUSSION... This morning`s satellite and radar imagery shows numerous showers across the state with showers mainly focused over windward and mountain areas, but select leeward areas are also seeing scattered showers this morning. Rainfall totals over the past 12 hours show the greatest amounts over the Ko`olau mountain on Oahu and on Mount Wai`ale`ale on Kauai with rainfall amounts of around 3 inches. Trade winds have significantly decreased over the past 24 hours with moderate east to east-southeast winds at best over select windward areas. For many leeward areas, winds remain light this morning, which should allow sea breezes to develop late this morning into the afternoon. Thus, I have updated the forecast to increase the chances for precipitation across leeward areas this afternoon. Afternoon convection across leeward and mountain areas could produce some moderate rain later today across the state. For Sunday, we should see much drier conditions compared to today as a drier air mass moves in from the east. A trough to the northwest of the state will continue to keep winds light to moderate and out of the east-southeast direction. Sea breezes developing during the day time should lead to afternoon clouds with some scattered showers over leeward areas. Due to the drier air mass, any rainfall should remain light with the exception of Kauai, where moderate afternoon showers will be possible due to lingering moisture. But overall shower activity should be much less than today across the state for Sunday. For early next week, high pressure will be centered far northeast of the state, while a trough lingers north of the state. We will continue to see light winds across the western half of the state, with light to moderate east to east-southeast flow over the eastern half of the state. Due to limited moisture, we are not expecting much rainfall early next week, but some light passing showers should be expected over windward areas, as well as some light showers over leeward areas during the afternoon with the sea breezes developing each day. For the second half of next week, guidance continues to show a some discrepancies between the ECMWF and the GFS. The ECMWF shows a much deeper upper level trough with a surface trough developing near the state. This setup would continue the hybrid tradewind and land/seabreeze pattern. Meanwhile, the GFS shows a much weaker upper level trough, with the surface high north of the state with strengthening trade winds during the second half of the week. The forecast as been updated to favor GFS for now, but will likely change over the next several days as model guidance narrows on a solution. && .AVIATION... Moist ESE flow has resulted in a wide coverage of light to moderate showers mainly over windward and mauka areas of all the islands. The exception is Oahu where showers have also filled in leeward. Periods of MVFR cig/vsby in SHRA may briefly be punctuated by short-lived IFR in heavier showers. Guidance indicates these conditions will persist through today, though some improvement will be possible during the peak heating hours. Finally, veering low-level flow is forecast to support the development of the "Maui vortex" by this afternoon, which typically impacts Kahului airport (PHOG) with significant low- level wind shear. AIRMET Tango for lee turb will likely be allowed to expire late this morning. AIRMET Sierra remains in effect for Kauai and Oahu as well as windward sections of Molokai and Kauai. && .MARINE... High pressure far northeast of the state will drive breezy east southeast winds today, while an approaching front lies far to the northwest. Winds are forecast to weaken in the coming days as the front approaches and the high shifts away to the east before moving back in around midweek. A Small Craft Advisory (SCA) for winds will remain in effect for most waters and channels surrounding Big Island, Maui, and Molokai through Sunday, but will likely end by Monday as winds weaken. Surf heights will remain below advisory thresholds for all shores through the forecast period. A small northwest, medium-period swell is forecast to subside this evening with only minor swells through next week. Breezy trade winds will produce choppy surf along east facing shores today, but will decrease as winds taper off in the coming days. Small, short-period southeast, and small medium-period south swell will continue into next week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Sunday for Maui County Windward Waters-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters. && $$ DISCUSSION...Kino AVIATION...JVC MARINE...Foster