Hilo

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 60 to 67 near the shore to 49 to 55 at 4000 feet. Light winds. Chance of rain 50 percent.

Friday: Sunny with isolated showers. Highs 77 to 82 near the shore to 63 to 69 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy with isolated showers. Lows 61 to 68 near the shore to 50 to 55 at 4000 feet. Light winds. Chance of rain 20 percent.

Kona

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 70 near the shore to 44 to 51 near 5000 feet. Light winds. Chance of rain 40 percent.

Friday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Friday Night: Mostly clear. Lows around 70 near the shore to 44 to 50 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy. Isolated showers in the evening. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the afternoon. Highs 63 to 82. East winds up to 15 mph. Chance of rain 20 percent.

Friday Night: Mostly clear. Isolated showers after midnight. Lows 61 to 69 near the shore to 52 to 60 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy. Isolated showers in the evening. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the afternoon. Highs 63 to 82. East winds up to 15 mph. Chance of rain 20 percent.

Friday Night: Mostly clear. Isolated showers after midnight. Lows 61 to 69 near the shore to 52 to 60 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy with scattered showers. Lows around 71 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs around 83 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Friday Night: Mostly clear. Lows around 72 near the shore to around 50 near 5000 feet. Northeast winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 60 to 67 near the shore to 49 to 55 at 4000 feet. Light winds. Chance of rain 50 percent.

Friday: Sunny with isolated showers. Highs 77 to 82 near the shore to 63 to 69 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Friday Night: Partly cloudy with isolated showers. Lows 61 to 68 near the shore to 50 to 55 at 4000 feet. Light winds. Chance of rain 20 percent.

Waikoloa

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 68 to 73 near the shore to 47 to 52 above 4000 feet. Light winds becoming southeast up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 82 to 87 near the shore to 64 to 71 above 4000 feet. North winds up to 10 mph. Chance of rain 40 percent.

Friday Night: Mostly clear. Lows 68 to 74 near the shore to 47 to 52 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

A front, currently over the Kauai Channel, will continue to bring increased shower activity to the western half of the state through Friday as it stalls and weakens near Oahu tonight through Friday. Breezy north-northeast winds will fill in behind the front tonight into Friday morning, then weaken and shift out of the east-northeast state- wide on Friday. Winds will briefly become light and variable over the weekend, before strong and gusty trades return for much of next week.

Discussion

Current radar and satellite imagery show a weakening pre-frontal low cloud and shower band just northwest of Oahu with the front over the Kauai Channel. High-resolution models seem to have a good handle on the location of the location of the front and shower band. They have the front slowing down as it approaches Oahu this evening, then stalling out and weakening in the vicinity of Oahu tonight through Friday. The moisture associated with this boundary will hang around, resulting in widespread showers over and around Oahu, and more scattered back over Kauai behind the front. The upper- level shortwave will wash out and lift northeastward tonight, taking the best dynamics and thunderstorm chances with it.
Gusty north to north-northeast winds are filling in behind the front over Kauai this afternoon and will spread eastward over Oahu tonight into Friday. Winds will gradually weaken and veer out of the east through the day Friday, statewide, as the residual frontal moisture retreats back westward. A brief return of light trade winds is possible over the weekend as another front passes to the north. Global long-range models are depicting increasing likelihood of strong easterly trades building in early next week as high pressure builds to the north in the wake of this passing boundary. These strong trades could last through much of next week.

Aviation

This afternoon, a front is located in the Kauai Channel, which has significantly increased showers and low clouds across the western end of the state today. Frequent IFR visibilities have been common within showers moving over Kauai since late morning. Additionally, winds have switched to become northerly behind the front, while moist southerly flow prevails ahead of it.
Guidance shows that the front will progress eastward and over Oahu this evening, then eventually wash out as residual moisture associated with the front retreats westward. Meanwhile, VFR conditions are expected to prevail throughout the next 24 hours across Maui County and the Big Island.
AIRMET Sierra for IFR conditions remains in effect for Kauai this afternoon. While conditions are expected to improve a bit for Kauai this evening, mountain obscuration will likely be an issue for the western end of the state through tonight.

Marine

A weakening front will stall and dissipate near Oahu tonight and Friday. High pressure building north of the area will produce fresh to locally strong northeast winds to the west of the front where a Small Craft Advisory is posted for both strong winds and rough seas through Friday.
Gentle east to southeast will persist over waters around Maui and Hawaii Counties tonight. There will be a brief period of moderate trade winds statewide late Friday as the front dissipates, but this will be short-lived. Winds will weaken and veer as the high moves away on Saturday. New high pressure building north of the area will lead to an increasing trade wind flow Sunday and Monday.
Northwest swell will continue to move through island waters over the next several days, keeping surf elevated along exposed north and west facing shores. A High Surf Advisory has been posted for north and west facing shores of Niihau and Kauai through Friday due to a jump at the Hanalei buoy late this afternoon. A fresh pulse of medium-period north northwest swell may arrive on Saturday, with another pulse possible on Monday.
Elsewhere, a small south swell will continue to diminish through tomorrow. Another long-period south swell is expected by this weekend.

Fire weather

Critical fire weather conditions are not anticipated due to increased moisture and rainfall chances associated with a cold front moving into the area and stalling today through Friday, and weaker winds through the weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Friday for Niihau, Kauai Leeward, Kauai North.
Small Craft Advisory until 6 PM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters.

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Data Courtesy of NOAA.gov