Hilo

Today: Breezy. Mostly cloudy with scattered showers. Highs around 82 near the shore to 68 to 73 at 4000 feet. Southeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 69 to 74 near the shore to around 59 at 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with scattered showers in the morning, then mostly cloudy with numerous showers in the afternoon. Highs around 81 near the shore to around 70 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 87 near the shore to around 71 near 5000 feet. Northeast winds up to 10 mph shifting to the west in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 75 near the shore to 53 to 58 near 5000 feet. North winds up to 10 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers in the morning, then cloudy with scattered showers in the afternoon. Highs around 86 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Mostly cloudy. Numerous showers in the morning, then showers in the afternoon. Highs 78 to 84 near the shore to 72 to 81 near 3000 feet. East winds up to 15 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 67 to 72 near the shore to 60 to 65 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Saturday: Cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 76 to 82 near the shore to 70 to 78 near 3000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Kohala

Today: Mostly cloudy. Numerous showers in the morning, then showers in the afternoon. Highs 78 to 84 near the shore to 72 to 81 near 3000 feet. East winds up to 15 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 67 to 72 near the shore to 60 to 65 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Saturday: Cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 76 to 82 near the shore to 70 to 78 near 3000 feet. East winds up to 15 mph. Chance of rain 70 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 74 near the shore to around 54 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Breezy. Mostly cloudy with scattered showers. Highs around 82 near the shore to 68 to 73 at 4000 feet. Southeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 69 to 74 near the shore to around 59 at 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with scattered showers in the morning, then mostly cloudy with numerous showers in the afternoon. Highs around 81 near the shore to around 70 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 89 near the shore to 69 to 77 above 4000 feet. East winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 76 near the shore to 56 to 61 above 4000 feet. Light winds. Chance of rain 50 percent.

Saturday: Mostly sunny in the morning, then cloudy with scattered showers in the afternoon. Highs 82 to 88 near the shore to 67 to 75 above 4000 feet. Light winds. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A kona low north of the state will continue drawing unstable tropical moisture northward over the islands into Saturday. Bands of showers producing moderate to heavy rain and isolated thunderstorms will move over the central and western islands tonight through at least Friday. The kona low will begin to drift away from the state this weekend with improving trends spreading from east to west. Enhanced rainfall may linger over Kauai and Niihau into Sunday. By Monday all islands will see a dramatic improvement in weather conditions as easterly trade winds return.

Discussion

A kona low northwest of the Hawaiian Islands will begin to slowly drift north away from the state today. A low level trough currently over Oahu will continue to produce periods of moderate to heavy showers across the western islands into the evening hours. Most of the heavy rain and flooding threat will occur along this trough shower band. The highest 24 hour rainfall totals over Oahu have reached around 10 inches in some locations. A Flood Watch remains in effect for the western islands into the evening, the Flood Watch for Oahu may be cancelled later today as this shower band moves westward into the Kauai Channel.
The latest satellite and local radar imagery this morning shows this shower band moving slowly westward through Oahu this morning where continued rainfall is expected until around mid morning. This shower band will then move into the Kauai Channel and approach Kauai from the east. Shower activity over Kauai will increase from late morning through the overnight hours as this shower band slowly moves over the garden isle. Rainfall rates under this band are falling up to 1 inch per hour.
Saturday and Sunday…The high pressure ridge will slowly build in north of the island chain this weekend, as the kona low exits the pattern to the north. Expect more stabilizing trends with decreasing showers as east to southeast winds spread across the state. By Sunday, the moderate to heavy rainfall threat will diminish over Kauai as more stable conditions fill in across the state.
Monday through Wednesday…More typical easterly trade winds return across Hawaii nei from Monday onward with only brief passing showers in the forecast favoring the typical windward and mountain areas through the middle of next week.

Aviation

A strong kona low NNW of Kauai is pulling tropical moisture out of the south across the state. This will keep the the islands in an showery weather pattern through the weekend. Moderate to heavy rain showers and isolated embedded thunderstorms are expected over the western side islands through this evening. On the Big Island, shower activity will taper off during the nighttime hours only to redevelop during the afternoons and early evenings.
Latest radar imagery reveals the heaviest showers over Oahu and the Kaiwi channel. This band is expected to slide gradually westward. By this evening, the heaviest showers will likely be over Kauai and Kauai Channel.
AIRMET Sierra is in effect for Kauai, Oahu, Molokai, Lanai, and windward Big Island. IFR conds over Kauai, Oahu, Molokai and Lanai will likely improve towards noon, but mountain obscuration will likely remain an issue for Oahu and Kauai through twenty-four hours.
AIRMET Tango is in effect for low level mechanical turbulence north through east of the Big Island and East Maui.
Occasional light rime icing is expected from Kauai to Molokai in layer 140-FL250.

Marine

Fresh to locally strong south to southeast winds associated with a kona low north-northwest of the state will persist through tonight. A shift out of the east to southeast direction is expected over the weekend through early next week as it lifts northward and away from the area. A Small Craft Advisory remains in effect for the Windward and Leeward Big Island waters (Hamakua Coast and waters near South Point) through tonight. In addition to the winds, expect locally rough seas in heavy showers or storms that develop, with the best chances being over the waters west of Maui County. Seas should remain just below the advisory level over the exposed Kauai waters as a short-period northwest swell moves through (downward trend expected this weekend).
Surf along south facing shores will remain up through early next week due to overlapping, long-period south-southwest swells expected. The first swell has filled in and will peak today, likely holding at the advisory level into Saturday before briefly lowering. Observations at offshore buoys 51003 and 51004 (51002 remains down) reflect this with the long-period peak energy now in the 15-17 second bands. Expect rough conditions for most southerly exposures today due to a combination of the onshore winds, swell, and periodic heavy showers moving through. As a result, a High Surf Advisory remains in effect through Saturday. A fresh, long-period south-southwest swell will begin to fill in through the day Sunday, then peak at a similar level early next week before easing through midweek.
Surf along north and west facing shores will remain up into Saturday due to a short-period northwest swell generated from the kona low. This swell will lower over the weekend.
Surf along east facing shores will remain well below average through the weekend. An upward trend is possible next week as the trades return locally and far upstream over the eastern Pacific.

HFO Watches/Warnings/Advisories

Flood Watch through this evening for Kauai, Niihau and Oahu.
Wind Advisory until 6 PM HST this evening for Big Island Summits.
High Surf Advisory until 6 PM HST Saturday for south facing shores.
Small Craft Advisory until 6 AM HST Saturday for Big Island Windward Waters, Big Island Leeward Waters.

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Data Courtesy of NOAA.gov