Hilo

Today: Frequent showers in the morning, then showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 75 to 80 near the shore to 61 to 66 at 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 62 to 69 near the shore to around 55 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Monday: Cloudy with showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 75 to 80 near the shore to around 63 at 4000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Kona

Today: Mostly cloudy. Isolated showers and thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening. Locally heavy rainfall possible in the evening. Lows 68 to 73 near the shore to 49 to 55 near 5000 feet. Light winds. Chance of rain 40 percent.

Monday: Mostly cloudy. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 81 to 86 near the shore to around 65 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Cloudy and breezy. Numerous showers in the morning, then showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 62 to 84. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 90 percent.

Tonight: Breezy. Showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 61 to 66 near the shore to 54 to 62 near 3000 feet. East winds 10 to 25 mph. Gusts up to 45 mph in the evening. Chance of rain near 100 percent.

Monday: Breezy. Cloudy with showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 61 to 82. East winds 15 to 25 mph. Chance of rain 90 percent.

Kohala

Today: Cloudy and breezy. Numerous showers in the morning, then showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 62 to 84. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 90 percent.

Tonight: Breezy. Showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 61 to 66 near the shore to 54 to 62 near 3000 feet. East winds 10 to 25 mph. Gusts up to 45 mph in the evening. Chance of rain near 100 percent.

Monday: Breezy. Cloudy with showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 61 to 82. East winds 15 to 25 mph. Chance of rain 90 percent.

South Big Island

Today: Mostly cloudy. Windy. Isolated showers and thunderstorms in the afternoon. Highs around 82 near the shore to around 65 near 5000 feet. East winds 10 to 30 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Windy. Scattered showers and isolated thunderstorms in the evening, then isolated showers after midnight. Locally heavy rainfall possible. Lows around 71 near the shore to around 51 near 5000 feet. East winds 15 to 30 mph decreasing to 10 to 20 mph after midnight. Chance of rain 30 percent.

Monday: Mostly cloudy. Breezy. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 80 near the shore to around 63 near 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Puna

Today: Frequent showers in the morning, then showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 75 to 80 near the shore to 61 to 66 at 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 62 to 69 near the shore to around 55 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Monday: Cloudy with showers and slight chance of thunderstorms. Locally heavy rainfall possible. Highs 75 to 80 near the shore to around 63 at 4000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Waikoloa

Today: Mostly cloudy. Breezy. Isolated showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 78 to 87 near the shore to 64 to 70 above 4000 feet. Northeast winds up to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with isolated showers and thunderstorms. Lows 67 to 73 near the shore to 49 to 55 above 4000 feet. East winds up to 25 mph with gusts to 45 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Monday: Mostly cloudy. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 78 to 86 near the shore to 63 to 68 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Strong trade winds will decrease slightly by Tuesday but remain breezy through the rest of the week. An upper trough approaching from the west will destabilize our weather this afternoon through the rest of the forecast period. Showers will increase today into tonight, with wet and breezy trade wind weather expected through the first half of the new week. Locally heavy rainfall is possible over windward areas this evening through Monday.

Discussion

High clouds continue to stream northeastward across the main Hawaiian Islands, but have decreased in coverage since last evening when they completely blocked the view of lower clouds. Marking the eastern flank of an upper trough, high clouds will likely stick around into next week as the upper trough drifts eastward. Radar shows scattered to numerous showers embedded within strong trade wind flow, favoring windward areas.
An unstable pattern will develop as the approaching upper trough pinches into an upper low just north of the chain, then lingers nearby through much of the forecast period. Models show an area of enhanced low level moisture will be near the Big Island later this morning. This moisture will spread westward to the smaller islands by tonight. The combination of increased moisture and increased instability will enhance showers over windward areas with the potential for showers to anchor along terrain. Leeward areas should see scattered showers as well from time to time today.
The Big Island will have the greatest chance for heavy rainfall and isolated thunderstorms this afternoon through Monday, with this chance tapering off farther to the west. East Maui may also be affected. This setup may continue through the middle of the week as the upper low lingers in the area. The threat for heavy rain and isolated thunderstorms will depend on the location and strength of the forecast upper low. Models show the upper low lingering nearby through Thursday. There are still some uncertainties regarding the strength and position of the low but, with unstable conditions expected, we should see showery conditions this week, especially across windward areas.

Aviation

Moderate to locally strong trade winds will continue to settle in across the islands through the weekend, as a large area of high pressure builds north of the state. This pattern will concentrate a majority of clouds and showers along east/northeast facing windward slopes, coasts, and within channels between islands through the TAF period. However, expect increasing chances for some showers to be forced leeward later this afternoon and evening in response to strengthening winds. Additionally, weaker gradient flow near sheltered leeward areas, will allow for sea breeze clouds and isolated showers again this afternoon across interior sections of mainly the the Big Island. Expect mainly VFR conditions into the afternoon, with periodic MVFR cigs this morning increasing in areal coverage as conditions continue to deteriorate toward AIRMET Sierra criteria.
AIRMET Tango for low-level mechanical turbulence immediately south through west of higher terrain, remains in effect for all islands. Also, a period of light ice could potentially develop in a shallow layer between FL180/280 today, mainly stretching from Maui to the Big island, as mid and upper lvl moisture continues to lift up across the islands.

Marine

High pressure northeast of the area is producing breezy to locally windy trade winds across the area. A Small Craft Advisory (SCA) is expanded to included all Hawaiian Coastal Waters through Monday.
The current small, short period northwest swell will linger through tonight. A larger and longer period northwest swell is expected to arrive Monday. The swell will then get a reinforcement late Tuesday into Wednesday with surf heights possibly reaching low end advisory levels. This swell will then lower gradually through the remainder of the week.
Small, mainly background south swells are expected today. A slightly larger and long period south swell is then expected to arrive tonight and Monday, then linger on into Tuesday. An even larger south swell is then expected to arrive by Wednesday. Data from the Aunuu Buoy in American Samoa indicates that this well is running higher than model guidance. This swell may be large enough for surf heights to reach low end advisory levels during its peak late Wednesday and Thursday. This swell will then lower gradually through the remainder of the week.
Trade winds over and upwind of the state will continue to produce short period choppy surf along east facing shores through the weekend and on through all of next week. Surf heights are expected to remain below advisory levels.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters,

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Data Courtesy of NOAA.gov