Hilo

Today: Mostly cloudy. Showers likely in the morning, then showers likely and slight chance of thunderstorms in the afternoon. Highs around 81 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 67 near the shore to around 53 at 4000 feet. North winds up to 20 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 80 near the shore to 65 to 70 at 4000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs 81 to 86 near the shore to around 72 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 85 near the shore to around 71 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Partly sunny. Windy. Showers likely in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 65 to 81. East winds 10 to 30 mph. Chance of rain 70 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 66 near the shore to 51 to 60 near 3000 feet. East winds 10 to 30 mph. Chance of rain 50 percent.

Thursday: Windy. Partly sunny with scattered showers. Highs 64 to 80. East winds 10 to 30 mph. Chance of rain 50 percent.

Kohala

Today: Partly sunny. Windy. Showers likely in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 65 to 81. East winds 10 to 30 mph. Chance of rain 70 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 66 near the shore to 51 to 60 near 3000 feet. East winds 10 to 30 mph. Chance of rain 50 percent.

Thursday: Windy. Partly sunny with scattered showers. Highs 64 to 80. East winds 10 to 30 mph. Chance of rain 50 percent.

South Big Island

Today: Windy. Mostly sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 84 near the shore to around 73 near 5000 feet. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 68 near the shore to around 53 near 5000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs around 83 near the shore to around 72 near 5000 feet. East winds up to 25 mph. Chance of rain 30 percent.

Puna

Today: Mostly cloudy. Showers likely in the morning, then showers likely and slight chance of thunderstorms in the afternoon. Highs around 81 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 67 near the shore to around 53 at 4000 feet. North winds up to 20 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 80 near the shore to 65 to 70 at 4000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny. Windy. Slight chance of thunderstorms and isolated showers in the afternoon. Highs around 83 near the shore to 67 to 74 above 4000 feet. Northeast winds up to 30 mph. Chance of rain 20 percent.

Tonight: Windy. Partly cloudy with isolated showers. Lows around 70 near the shore to 48 to 56 above 4000 feet. East winds up to 30 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Windy. Isolated showers in the afternoon. Highs around 82 near the shore to 66 to 73 above 4000 feet. Northeast winds up to 30 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weakening stationary front near Kauai will gradually dissipate over the next couple days, keeping shower coverage higher over the Garden Isle, while fairly typical trade wind weather prevails over the rest of the state. The remnant moisture from the old front will slide southeastward down the island chain Friday through Saturday, bringing an increase in showers to mainly windward areas as it moves through. A new front could bring an an increase in showers once again as it moves into the islands from the north Sunday, then stalls out and gradually dissipates early next week. Breezy to windy trades will prevail through Friday, trend downward over the weekend, then lower further early next week.

Discussion

Currently at the surface, a weakening stationary front is oriented southwest to northeast and is positioned near Kauai. Meanwhile, a pair of high pressure systems are located to the distant northwest and distant northeast. These high pressure systems are dominating the local pressure gradient and producing breezy trade winds across the island chain early this morning. Aloft, a southwest to northeast oriented upper level trough is positioned over the western islands, and is resulting in scattered to broken high clouds across the state. Partly to mostly cloudy conditions prevail, with sky coverage the greatest in windward areas. Radar imagery shows scattered to numerous showers moving into windward areas, with coverage the greatest over Kauai and the Big Island. A few of these showers are making the trip over the mountains and into leeward communities at times as well. Main short term focus revolves around rain chances statewide, and thunderstorm potential over the Big Island.
High pressure northwest of the islands will remain nearly stationary through Friday, while the front over Kauai weakens into a trough later today, then dissipates on Thursday. This will keep breezy trade winds in place through the end of the work week, with windy conditions expected Thursday. There is the potential that some of the typically windier areas could see winds reach advisory levels on Thursday as well. The trades will trend downward into the moderate range over the weekend, then lower further into the light to locally moderate range early next week.
As for the remaining weather details, with the troughing aloft beginning to weaken and not aligning with the deepest moisture, the potential for flash flooding over Kauai has diminished. As a result, the Flood Watch has been cancelled. The highest shower coverage is expected over Kauai today in the vicinity of the weakening stationary front. Elsewhere, from Oahu eastward to the Big Island, more typical trade wind weather can be expected with scattered showers favoring windward terrain along with the occasional leeward spillover. Additionally, an isolated thunderstorm or two could pop this afternoon over the Big Island, similar to what happened yesterday.
The upper troughing will continue to weaken as it slides southeastward tonight and Thursday, with mid-level riding building in behind it and holding in place through early next week. A surface trough will remain in place near Kauai tonight, before dissipating Thursday. A lingering band of moisture however will remain in the vicinity of Kauai Thursday and Thursday night, with models then advertising this moisture band sliding southeastward down the island chain Friday through Saturday although progression details differ. This should keep shower coverage the highest over Kauai through Thursday night, with more typical trade wind shower coverage over the other islands. We should then see an increase in trade wind showers as the moisture band slides southeastward down the island chain Friday through Saturday, with windward locales remaining the main targets. A new front is forecast to approach from the north Saturday night, and could bring an increase in shower activity particularly to windward sections of the islands Sunday. The front is expected to stall out and gradually dissipate early next week. At the same time, weakening trade winds will bring a hybrid trade wind and land/sea breeze pattern which could lead to more leeward afternoon and early evening shower activity.
Finally, high clouds will continue to stream over the islands today, but should be thinning out as the day progresses. The high clouds should exit to the east of the state by Thursday.

Aviation

A weakening nearly stationary frontal boundary remains in the vicinity of Kauai early this morning. Surface high pressure far northwest of the region is producing strong low-level trade winds across the state. Broken low clouds with embedded scattered showers, which are related to the moisture along and east of the frontal boundary, are being transported by the low-level trade flow into Kauai and windward Oahu. Periods of MVFR conditions due to low ceilings and reduced visibilities are expected today over most of Kauai, and over windward Oahu. AIRMET Sierra remains in effect for mountain obscuration on Kauai and Oahu. Elsewhere, expect brief periods of MVFR conditions along windward sections of the islands east of Oahu.
The high clouds, which were very extensive over Kauai and Oahu last evening, have been thinning during the past few hours. Therefore, the threat of light rime icing in clouds from Kauai to Oahu, which was noted in AIRMET Zulu, may be less likely later this morning.
Finally, the strong trade winds will likely persist for the next couple of days. Therefore, AIRMET Tango remains in effect for moderate low-level turbulence below 8 thousand feet downwind of the higher terrain on all islands. This AIRMET will likely be required at least through early Thursday morning.

Marine

A high pressure system north of the state and a weakening stationary front near Kauai will keep fresh to strong trade winds in the forecast into Friday. An upper level disturbance will produce passing showers through the week with isolated thunderstorms possible near Kauai waters through daybreak. A Small Craft Advisory (SCA) remains in effect for all waters today and Thursday for a combination of strong winds and rough seas. This SCA will likely be extended for some of the windier waters into the weekend.
A pulse of north-northwest swell has arrived today as the northwest swell energy declines. Swell heights at north shore buoys are running 1 to 2 feet above GFS Wave model guidance. One foot was added to the north-northwest swell grids this morning to account for this lower model bias. The High Surf Advisory (HSA) was also extended today for north facing shores from Kauai to Maui. Harbor surges at Kahului and Hilo Harbors are possible today as northerly swell heights approach critical harbor thresholds. This swell will peak today and then slowly fade into the weekend.
Strong and gusty trades over and upstream of the islands will continue to drive wind and swell waves into east facing shores. Elevated surf heights will continue along east facing shores through Friday. An out of season south-southwest swell will also pass through the region over the next few days. This swell will continue to increase south shore surf heights above seasonal average heights this week. This south swell will peak later today and then slowly fade into the weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST Thursday for all Hawaiian waters,

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Data Courtesy of NOAA.gov