171 FXHW60 PHFO 141302 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 302 AM HST Mon Apr 14 2025 .SYNOPSIS... Breezy trade winds will continue today and gradually ease tomorrow, with passing clouds and showers favoring windward and mauka areas. Lighter winds are expected by the middle of the week with fewer windward showers and a greater chance for afternoon interior showers through the weekend. An upper level trough and deep atmospheric moisture will enhance shower activity on Thursday and Friday and bring the potential for heavy rainfall. && .DISCUSSION... This morning`s radar and infrared satellite imagery show a bit more shower activity compared to last evening, with scattered showers moving into windward and mauka areas across the island chain. High pressure centered to the northeast of the state will maintain breezy trade winds across the region through tonight, continuing to focus clouds and showers over windward and mauka areas. In addition, water vapor imagery shows a weak upper-level low spinning over the state, which will provide a modest amount of instability aloft. Model guidance shows that this upper low will gradually move across the state through Tuesday contributing to a slow eastward spreading of weak instability, which may allow for the enhancement of windward showers moving in on the breezy trades. Some of these showers could deliver brief downpours that will occasionally spill over into leeward areas. Mid-level ridging will briefly build overhead late tomorrow into early Wednesday in advance of a mid-level shortwave trough that will dive southeast across the Central Pacific and begin to edge over Hawaii by Wednesday night. At the surface, a strong low pressure system to the far north will displace the ridge that`s been anchored to our northeast to bring it closer to, or over, the island chain. The proximity of this ridge axis and the approach of a cold front from the northwest will bring lighter southeast winds across the area, allowing land and sea breezes to expand in coverage beginning on Wednesday. The shortwave trough will dive down the island chain through the latter part of the week before it opens up and weakens heading into early next week. The most favorable upper-level dynamics associated with the orientation of the shortwave trough, the coolest temperatures aloft (around -12C), and the deepest atmospheric moisture (precipitable water around 1.6 inches) all seem to line up best on Thursday and Friday. As such, the potential for heavy showers will be greatest on Thursday and Friday afternoons with the sea breeze activity. Light winds will continue into the weekend as the mid-level shortwave weakens resulting in either a land/sea breeze pattern with more muted diurnal convection or a hybrid sea breeze pattern which will tend to focus showers over western slopes of each island. && .AVIATION... Breezy trade winds will steer bands of clouds and light showers off the Pacific towards the Islands. Showers will be most active in the late night and morning hours and favor windward slopes and coasts. AIRMET Tango remains in effect for occasional moderate turbulence below 8000 feet over and along the lee side of all Hawaiian islands and is expected to remain necessary through early evening and possibly beyond. && .MARINE... High pressure northeast of the state will maintain moderate to strong trades through tonight. A Small Craft Advisory (SCA) is now in effect for the eastern half of the marine area through 6 AM Tuesday. The SCA may eventually need to be extended through Tuesday for some zones on the Big Island favored in an east- southeast flow. The trades will gradually ease Tuesday and Tuesday night, then become further disrupted Wednesday through Friday as a front approaches, stalls out, and dissipates northwest of the state. Winds will become light and variable during the mid to late week time frame over the western waters, while winds over the eastern end of the state shift out of the east-southeast at light to moderate speeds. A small to moderate sized northwest swell will give a boost to surf along north and west facing shores today and tonight, followed by a decline Tuesday and Wednesday. A new moderate-sized north-northwest swell will arrive Thursday, potentially bringing advisory level surf to north and west facing shores Thursday night and Friday, then slowly lowering over the weekend. East shore surf will remain at or just above average through Tuesday, and will be rather rough due to the strong trades, today. As the trades diminish during the second half of the week, surf along east facing shores will drop below normal. Surf along south facing shores will remain small and mostly at background levels through Thursday. A series of small overlapping south swells could bring surf up to seasonal levels Friday through next weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Tuesday for Kaiwi Channel- Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Farris AVIATION...Bedal MARINE...Jelsema