Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 77 to 82 near the shore to around 67 at 4000 feet. Southwest winds around 10 mph shifting to the east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows 61 to 69 near the shore to around 54 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 60 percent.

Thursday: Partly sunny with scattered showers. Highs 76 to 81 near the shore to around 66 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Mostly cloudy. Showers likely and slight chance of thunderstorms in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. North winds around 10 mph shifting to the west up to 10 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows 67 to 72 near the shore to 45 to 53 near 5000 feet. Light winds. Chance of rain 20 percent.

Thursday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Waimea

Today: Partly sunny. Breezy. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 63 to 83. Southeast winds 10 to 15 mph shifting to the east 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 65 near the shore to 52 to 60 near 3000 feet. East winds 10 to 15 mph increasing to 10 to 25 mph after midnight. Chance of rain 50 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 63 to 83. East winds 10 to 25 mph. Chance of rain 50 percent.

Kohala

Today: Partly sunny. Breezy. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 63 to 83. Southeast winds 10 to 15 mph shifting to the east 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 65 near the shore to 52 to 60 near 3000 feet. East winds 10 to 15 mph increasing to 10 to 25 mph after midnight. Chance of rain 50 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 63 to 83. East winds 10 to 25 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly cloudy. Breezy. Scattered showers and slight chance of thunderstorms in the afternoon. Highs around 81 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 70 near the shore to around 49 near 5000 feet. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Thursday: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 82 near the shore to around 67 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 77 to 82 near the shore to around 67 at 4000 feet. Southwest winds around 10 mph shifting to the east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows 61 to 69 near the shore to around 54 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 60 percent.

Thursday: Partly sunny with scattered showers. Highs 76 to 81 near the shore to around 66 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Mostly cloudy. Showers likely and slight chance of thunderstorms in the afternoon. Highs 79 to 86 near the shore to 64 to 69 above 4000 feet. South winds around 10 mph shifting to the northwest in the afternoon. Chance of rain 70 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows 65 to 73 near the shore to 46 to 53 above 4000 feet. Southeast winds up to 15 mph increasing to up to 25 mph after midnight. Chance of rain 20 percent.

Thursday: Sunny and windy. Highs 78 to 86 near the shore to 64 to 70 above 4000 feet. Northeast winds up to 30 mph increasing to 10 to 30 mph in the afternoon.

Detailed Forecast

Synopsis

Light to locally moderate east-southeast winds will deliver a few showers through Wednesday morning, some briefly heavy, mainly to windward areas. Sea breezes will allow clouds and showers to develop over leeward and interior areas on Wednesday afternoon. Increasing trade winds are expected from Wednesday night into the weekend, delivering just a few brief showers to windward areas, while leeward areas remain mostly dry. Trade winds may become very strong over the weekend, but will likely diminish again early next week.

Discussion

Low-level troughing persisting to the NW of the islands will keep trade winds on the lighter side, and veered to the ESE, through Wednesday. As the trough dissipates Wednesday night and Thursday, high pressure will build NW of the islands, and trade winds will increase as they back to the ENE. Trade winds will increase further over the weekend as the high passes N of the islands, with windy conditions potentially warranting a Wind Advisory. A trend toward lighter winds is expected early next week as the high moves to the distant NE of the islands, and a front weakens the associated ridge N of the islands.
Broken to overcast high clouds help to highlight the axis of a trough aloft over the islands, and have recently cleared Kauai and Oahu. This trough will continue to move steadily E, with high clouds likely to move E of all islands by the middle of the day tomorrow. The trough has brought some instability, and radar shows a few moderately heavy showers, with a weakened inversion evident in the 00Z sounding from PHLI.
The light to moderate ESE winds will deliver a few showers overnight and Wednesday morning, mainly to windward locales, but the slightly veered flow may allow a few showers to sneak into leeward areas. Additionally, the Kau District of the Big Island will continue to see moisture moving ashore. Moderate instability will allow for some brief heavy downpours. Sea breezes along leeward areas are likely to gain a little more vigor tomorrow as the high clouds will no longer limit the amount of daytime heating, with a few showers popping up. Increasing stability may limit the intensity of the rainfall on the smaller islands, but the heating and instability on the Big Island may be sufficient to produce a few afternoon thunderstorms over the slopes. Will monitor overnight trends to determine if they warrant inclusion in the morning forecast update.
Ridging aloft will likely lead to a relatively dry trade wind flow as winds increase, with passing light showers over windward areas occasionally spreading leeward, especially during nights and mornings. Forecast models are not detecting any organized moisture sources through the weekend, so significant rainfall accumulation is not expected. A trend toward increased instability is suggested by the guidance for early next week, but this solution has not been consistent from run to run.

Aviation

An area of high pressure north of the islands will reinforce southeast trade winds across the state through Wednesday, focusing showers and clouds along windward slopes. Diurnal circulations will continue over sheltered leeward areas through the period, with afternoon sea breeze clouds and showers that developed earlier, diminishing tonight as land breezes develop. Mostly VFR conditions are expected through the TAF period, however MVFR cigs and potential MVFR vsby, remain possible in developing showers especially windward Big Island.
AIRMET Tango continues for tempo moderate upper-level turbulence between FL280 AND FL400 across most of the state. These conditions are expected to slowly improve from west to east across the island as upper dynamics diminish and begin to exit the region.

Marine

Gentle to moderate east-southeast winds will continue through Wednesday, then shift out of the east and increase into the fresh to strong category Thursday as strong high pressure begins to build north of the area. The peak of the event is expected over the weekend, when the winds will near gale levels over the windier waters around Maui County and the Big Island as the high moves directly north of the state. Seas will respond and become rough through this time. Small Craft Advisory (SCA) conditions will be the result across the typical areas Thursday into Friday, then for all waters over the weekend due to a combination of winds and seas.
Surf along north and west facing shores will remain up near advisory levels into Wednesday as a north-northwest swell moves through. Offshore buoys appear to have peaked, but are holding in the 12-13 second band this evening. Heights should start to lower by the afternoon period Wednesday as this source begins to move out.
A new long-period, northwest swell associated with a large batch of gales that has setup around 1500 to 2000 nm northwest of the islands over the past 24-hrs will begin to build down the island chain and peak Friday. Heights may reach advisory levels for exposed north and west facing shores Friday into Saturday, before the swell gradually eases through the second half of the weekend.
Surf along east facing shores will trend up and become rough Friday through the weekend in response to the strong trades locally and upstream.
Surf along south facing shores will remain small through the weekend with mainly background pulses moving through periodically. The next pulse is expected over the weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov