Hilo

Tonight: Occasional showers. Lows 64 to 70 near the shore to 54 to 60 at 4000 feet. North winds up to 15 mph. Chance of rain near 100 percent.

Thursday: Occasional showers. Locally heavy rainfall possible. Highs 77 to 83 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Thursday Night: Occasional showers. Locally heavy rainfall possible in the evening. Lows 63 to 70 near the shore to 54 to 60 at 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Kona

Tonight: Partly cloudy. Lows around 74 near the shore to 49 to 54 near 5000 feet. Light winds.

Thursday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 84 to 89 near the shore to around 68 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Isolated showers in the evening. Lows around 75 near the shore to 49 to 55 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Occasional showers. Lows 64 to 72 near the shore to 56 to 63 near 3000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Thursday: Breezy. Occasional showers. Highs 65 to 83. East winds 10 to 25 mph. Chance of rain near 100 percent.

Thursday Night: Breezy. Occasional showers in the evening, then scattered showers after midnight. Lows 64 to 72 near the shore to 57 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Kohala

Tonight: Breezy. Occasional showers. Lows 64 to 72 near the shore to 56 to 63 near 3000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Thursday: Breezy. Occasional showers. Highs 65 to 83. East winds 10 to 25 mph. Chance of rain near 100 percent.

Thursday Night: Breezy. Occasional showers in the evening, then scattered showers after midnight. Lows 64 to 72 near the shore to 57 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

South Big Island

Tonight: Mostly clear. Breezy. Lows around 75 near the shore to around 53 near 5000 feet. Northeast winds 10 to 20 mph.

Thursday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 87 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 75 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Tonight: Occasional showers. Lows 64 to 70 near the shore to 54 to 60 at 4000 feet. North winds up to 15 mph. Chance of rain near 100 percent.

Thursday: Occasional showers. Locally heavy rainfall possible. Highs 77 to 83 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Thursday Night: Occasional showers. Locally heavy rainfall possible in the evening. Lows 63 to 70 near the shore to 54 to 60 at 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Waikoloa

Tonight: Partly cloudy. Breezy. Lows around 75 near the shore to 52 to 57 above 4000 feet. East winds up to 20 mph.

Thursday: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 90 near the shore to around 69 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Thursday Night: Partly cloudy. Scattered showers in the evening. Lows around 75 near the shore to 53 to 58 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure to the north will maintain moderate to locally breezy trade winds over the next few days. Increased showers favoring windward and mountain slopes will continue through Friday. Weaker trade winds with fewer showers are expected this weekend, with another round of increased showers next week.

Discussion

Some additional tweaks were made to the forecast since this morning. The area of clouds and showers immediately upstream of the central islands has thinned as was expected, but the high resolution models and the National Blend of Models have backed off a bit more on the showers for the central islands even tomorrow. The PoPs remain higher for Kauai, which is near the upper level trough, and the Big Island, which is closer the band of moisture riding in on the trades from the former Tropical Cyclone Kristy. Still expecting showers over the Big Island to possibly be locally heavy tomorrow, so that remains in the forecast, but not expecting any significant issues with this short lived enhanced rainfall.
Little change in the global models through the forecast period. In the near term, there is good agreement both at the surface and in the upper levels. A surface high to the north of the islands will maintain the moderate to locally breezy trades. An upper level trough over the western islands will lift north as an upper level low forms along the trough. Heading into the weekend, the high to the north begins to move to the east, causing our trades to weaken and turn first a bit more easterly, and then possibly a little more east-southeasterly. Showers should thin out a bit across the state for much of the weekend.
Heading into the new week, the global models remain in good agreement with the high to the northeast, and a cold front approaching the islands from the northwest. The main differences have to do with the mid to upper levels, and that could mean some differences in the amount of rainfall. Both the GFS and ECWMF bring the front at least partway down the island chain. With the differences in the deterministic models, have opted to use the National Blend of Models for the forecast to better capture the various model ensembles. Will be watching future model runs to see if better agreement is reached.

Aviation

Moderate to locally breezy trades will focus clouds and showers over windward and mauka areas through the forecast period, especially during the overnight to early morning hours. A plume of low level moisture will begin to move up the island chain from the southeast tonight and bring an uptick in clouds and showers to windward areas. MVFR conditions can be expected in moderate to heavy showers with brief IFR conditions possible.
AIRMET Sierra for mountain obscuration is in effect for windward portions of the Big Island. This AIRMET may need to be expanded to include some of the smaller islands overnight.
AIRMET Tango for moderate low level turbulence lee of island terrain remains in effect and will likely continue over the next 24 hours.

Marine

Fresh to strong easterly trades will continue through Friday, then potentially ease over the weekend as a weakness forms in the ridge to the north. A Small Craft Advisory is in effect for the typical windier zones and waters around Maui County and the Big Island through Friday.
A small north-northeast swell will lower Thursday into Friday. An upward trend is expected this weekend due to a storm-force low centered over the far western Bering Sea. Earlier satellite data showed a large swath of storm-force winds aimed at Hawaii within the 310-330 degree directional bands, with altimeter data near the heart of the fetch showing heights of up to 36 ft (a few feet higher than model guidance is depicting). Expect small, long- period forerunners to arrive around sunset Friday evening from the north- northwest, then building over the weekend with a peak now anticipated on Sunday. Heights could approach advisory levels for exposed north and west-facing shores during the peak, especially if the swell comes in higher than predicted.
Surf along east-facing shores will remain rough throughout the week due to the strong trades locally and upstream across the eastern Pacific. A downward trend is possible this weekend.
Surf along south-facing shores will remain small, with mainly a mix of short-period southeast and background long-period south swell energy.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov