Photo Credit: James Grenz

Hilo

Today: Partly sunny with scattered showers. Highs around 85 near the shore to around 72 at 4000 feet. South winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. South winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 82 to 88 near the shore to around 73 at 4000 feet. Southeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 85 near the shore to around 71 near 5000 feet. South winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows 69 to 75 near the shore to around 55 near 5000 feet. Southeast winds up to 10 mph shifting to the northeast after midnight. Chance of rain 20 percent.

Friday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 85 near the shore to around 71 near 5000 feet. Northeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Waimea

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 83 near the shore to 69 to 80 near 3000 feet. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 67 near the shore to 54 to 61 near 3000 feet. Light winds becoming south up to 10 mph after midnight. Chance of rain 40 percent.

Friday: Partly sunny with scattered showers. Highs around 84 near the shore to 75 to 82 near 3000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 83 near the shore to 69 to 80 near 3000 feet. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 67 near the shore to 54 to 61 near 3000 feet. Light winds becoming south up to 10 mph after midnight. Chance of rain 40 percent.

Friday: Partly sunny with scattered showers. Highs around 84 near the shore to 75 to 82 near 3000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs around 84 near the shore to around 74 near 5000 feet. Light winds becoming south around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows around 70 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 84 near the shore to around 74 near 5000 feet. East winds 15 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 85 near the shore to around 72 at 4000 feet. South winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. South winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 82 to 88 near the shore to around 73 at 4000 feet. Southeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 82 to 87 near the shore to 68 to 74 above 4000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 70 to 75 near the shore to 51 to 59 above 4000 feet. Light winds. Chance of rain 20 percent.

Friday: Sunny in the morning then becoming partly sunny. Isolated showers. Highs around 85 near the shore to 68 to 75 above 4000 feet. North winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A stalled front near Molokai is expected to weaken, and become a surface trough later this morning. Moderate northeast winds persist west of the front, while light and variable winds are over the eastern islands. Once it develops, the surface trough will move back toward the western end of the island chain from later today through Friday. This will likely keep a wet weather pattern across portions of the state, especially on Oahu and Kauai, during the next couple of days. Once this surface feature moves west of the islands, expect a more typical trade wind weather pattern to return to the state from this weekend into the middle of next week.

Discussion

Based on satellite imagery, radar reflectivity data, and surface observations, a weakening front appears to have stalled over Maui County near Molokai early this morning. An area of locally heavy rainfall developed over portions of Molokai late Wednesday evening. Some showers linger along the northeast coastal section of Molokai, but most of these showers have now moved over the coastal waters just north of eastern Molokai. A diffuse band of broken to locally overcast low clouds with embedded light showers remains draped across Oahu and Kauai to the west of the front. Moderate northeast winds also continue to the west of the front, while light and variable winds persist elsewhere. As a result, local nighttime land breezes, which become established last evening, dominate the flow over most of the Big Island and Maui. The showers west of the front will continue to favor north through northeast facing slopes of Oahu and Kauai through this morning.
There is an upper-level low centered near 33N 158W with an upper- level trough extending down over Oahu. This trough aloft will keep the atmosphere unstable over the western islands during the next few days as it tracks slowly westward. At the same time, the nearly stationary front will transform into a surface trough later this morning. The forecast guidance is in good agreement that the surface trough will begin to shift back slowly west toward Oahu by this afternoon. This will cause the winds to become lighter, and gradually shift out of the southeast across much of the area later today and tonight. The atmospheric instability due to the upper-level trough will persist over the western islands. This combined with the slightly enhanced moisture that will accompany the westward moving surface trough will produce passing showers as it moves over Oahu tonight, and then over Kauai on Friday. At the moment, we do not anticipate significant flooding due to widespread heavy rainfall in the forecast guidance. However, some locally heavy downpours cannot be ruled later today and/or Friday.
By Saturday, the surface trough will be departing to the west of Kauai. Surface high pressure will build to our north, which will allow moderate trade winds to gradually fill back in over the state this weekend. The trade winds are expected to persist into the middle of next week. Low clouds and showers transported by the trades into the islands will tend to favor windward and mauka areas, but the trade winds may transport light showers over to leeward sections of some of the smaller islands. A weak inverted upper-level trough is forecast to set up just east of the islands early next week, which may enhance some of the low clouds and showers as they arrive into the state. However, rainfall totals on any given day or night will be highly dependent on incoming moisture availability.

Aviation

A stationary front, currently situated near Molokai, will transition into a trough later today and retrograde westward across the state. This feature will bring layers of clouds and scattered to numerous showers to mainly interior portions of Oahu and Kauai. MVFR conditions may accompany this activity, see AIRMET SIERRA below. Elsewhere, isolated showers will prevail.
Light flow will allow for seabreeze development by late this morning and into the afternoon, especially along the more sheltered leeward coastal locations.
AIRMET SIERRA remains in effect above 2500 feet for north thru east sections of Kauai, Oahu, and Molokai for tempo mountain obscuration due to clouds and showers.

Marine

A front will stall and weaken to a trough around Maui County today. Southeast winds will develop over the eastern end of the state later today and usher the boundary west into tomorrow. A high will build far northeast of the state allowing strong to moderate trades to return to all waters by Saturday and hold into early next week.
A storm low located roughly 700 nm north of Kauai will continue to send a large, short period north swell towards the state through today. The High Surf Advisory has been extended for north facing shores of Kauai, Oahu and Maui County through tonight and may need to be extended for some zones later this afternoon. In addition, a Small Craft Advisory now in effect for most forecast waters due to continued elevated seas. Swell produce from this low will peak today, hold into tonight before steadily declining tomorrow into the weekend.
A series of moderate, long-period south swells will keep south facing shore surf elevated tonight through Saturday. With no significant trade wind flow over and upwind of the state, most surf along east facing shores will be from north swell wrap through the week. Moderate, choppy east shore surf will likely return over the weekend and persist into early next week as the trade winds return.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Friday for north facing shores of Kauai, Niihau, Oahu, Molokai and Maui
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

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Data Courtesy of NOAA.gov