Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
848 FXHW60 PHFO 171336 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 336 AM HST Tue Jun 17 2025 .SYNOPSIS... A broad high pressure ridge north of the Hawaiian Islands will keep breezy trade winds in the forecast today. Trade winds will decrease slightly from Wednesday through Friday, then become breezy once again this weekend. A few showers are possible in this pattern especially along the windward and mountain slopes, favoring the overnight to early morning hours. && .DISCUSSION... The infra-red satellite imagery this morning shows a few bands of unsettled clouds riding into the windward island mountains on the easterly trade winds. Expect periods of showers through the early morning hours over these mountain areas with shower trends decreasing by late morning into the afternoon. Upper air balloon soundings from Lihue and Hilo at 2 AM HST (12Z) this morning show temperature inversion heights in the 6,000 to 7,000 foot elevation range. These inversion heights support a fairly stable weather picture with brief passing showers possible. The short term wind forecast trends are higher for today than we anticipated in our model guidance from 24 hours ago. Therefore expect continued breezy trade winds for one more day before we shift to a lower speed gear as winds drop to more moderate levels from Wednesday through Friday. The high pressure ridge will then build in again by this weekend with wind speeds returning to breezy levels. Looking into the cloud and shower activity for the next seven days we continue to see subtle shifts in the day to night diurnal rainfall pattern through Friday with temperature inversion heights ranging from the 6,000 to 8,000 foot elevation range over this time period. Fairly stable conditions for the most part with some periods of passing showers mainly in the overnight to early morning hours as a few unsettled passing cloud bands are lifted up and rain over windward island mountains. These rainfall amounts will remain on the low side with the best chances for shower activity occurring during the typical overnight to early morning hours. More stable trends develop this weekend as the ridge builds back into the Hawaii Region, decreasing island cloud cover and shower trends. Finally, expect a subtle increase in shower trends by early next week as a combination of upper (500 mb) and lower level (700 mb) troughing move into the region. && .AVIATION... Breezy trade winds with brief passing showers will continue today. Wind speeds will decrease to more moderate levels from Wednesday onward. Shower activity will be limited to windward and mountain areas, favoring the overnight to early morning hours. AIRMET Sierra remains in effect for mountain obscurations along north and east slopes of Kauai, Oahu, Molokai, Maui and the Big Island. These low cloud ceilings will likely diminish later this morning. AIRMET Tango remains in effect for moderate turbulence over and south through west of island mountains. These stronger winds and turbulent conditions will likely continue into the evening hours. && .MARINE... High pressure north Hawaii will slowly move eastward today and drive fresh to strong trades across the local waters. Trades will weaken slightly Wednesday through the rest of the week as the aforementioned high becomes anchored northeast of the islands. A Small Craft Advisory (SCA) has been expanded through this evening to cover much of the coastal waters. However, for tonight and through the remainder of the week, the SCA will likely be scaled back to just the windier waters and channels near Maui and the Big Island. Surf along the south facing shores will be small today, as the current small, medium period, south swell fades. A small, long period, south swell will arrive on Wednesday and bring a slight bump up in surf through the weeks end. Rough and choppy conditions along east facing shores will continue this week. Surf will remain nearly flat along north facing shores throughout the forecast period. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters-Kauai Leeward Waters-Kauai Channel-Kaiwi Channel-Maui County Windward Waters. Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Bohlin AVIATION...Bohlin MARINE...JT