West Side

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 76 to 82. Southwest winds up to 10 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 72. Light winds becoming east up to 10 mph after midnight. Chance of rain 40 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 82. East winds up to 15 mph. Chance of rain 40 percent.

South Side

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85. Light winds. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 64 to 73. North winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs around 85. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

North Shore

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 69 near the shore to around 50 near 5000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 81 to 86. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 69. Northeast winds up to 10 mph. Chance of rain 40 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs 79 to 85. Northeast winds up to 15 mph. Chance of rain 40 percent.

Upcountry

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 64 at the visitor center to around 67 at the summit. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 45 at the visitor center to around 47 at the summit. Light winds becoming east up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Mostly sunny with scattered showers. Highs around 63 at the visitor center to around 65 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

East Maui

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 69 near the shore to around 50 near 5000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 70 to 78. Light winds. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 63. Light winds becoming northeast around 10 mph after midnight. Chance of rain 20 percent.

Friday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 71 to 78. Northeast winds up to 10 mph. Chance of rain 20 percent.

Kaunakakai

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 69 to 87. Light winds. Chance of rain 30 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 56 to 72. Light winds becoming east up to 10 mph after midnight. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs 67 to 86. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Southerly winds and increasing moisture ahead of an approaching front and upper disturbance will lead higher rainfall chances for portions of the state today through Friday. The front will reach Kauai later today, then stall and begin to diminish near Oahu tonight into Friday. Breezy north-northeast winds will fill in behind it over Kauai this afternoon, then shift out of the east- northeast Friday. The trades will briefly weaken over the weekend, before becoming strong and gusty early next week.

Discussion

Moist southerly flow and lift ahead of a cold front and an upper trough approaching from the northwest will lead to increasing rainfall chances today, particularly over the western end of the state. Early morning radar and satellite data show a pre-frontal low-cloud band with cooling tops and embedded showers lurking west of Kauai. High-resolution model reflectivities seem to be initializing well and depict this band becoming active with moderate to heavy showers through the morning hours as it advances eastward over Kauai. The better dynamics (35 to 45 kt 0-6 km shear) and upper height falls are expected later today over and around Kauai as the front draws closer and begins to move into the area. Although the chances are low, a few thunderstorms developing along and ahead of the front can't be completely ruled out over and around Kauai today. This threat appears less likely over the rest of the state.
The front will stall and slowly diminish around Oahu tonight through Friday as the shortwave trough begins to lift northeastward and away from the area. Gusty north to north- northeast winds trailing the front later today through tonight over the western end of the state will veer out of the east on Friday (statewide), with the residual moisture associated with the front retreating westward. A brief return of light trade winds is possible over the weekend as another front passes to the north. There is an increasing likelihood of strong easterly trades early next week as high pressure builds to the north in the wake of this passing boundary.

Aviation

A front is approaching Kauai and will stall around Oahu later tonight and into Friday. Winds will increase and veer from southerly to NNE behind the front. SHRA and low cigs will be possible particularly along the western end of the state. MVFR conds can be expected in SHRA with some possible IFR conds in heavier showers. There is a chance for some ISOL TSTMs near Kauai. VFR should generally prevail outside of SHRA/TSTMs.
AIRMET Sierra is in effect for mtn obsc for W thru S locations of Kauai and Oahu.

Marine

A fairly robust cold front approaching Kauai this morning will bring some changes to our recent light wind weather pattern, primarily to waters around Kauai and Oahu. The front just moved over NDBC buoys 51101 and 51001 NW of Kauai, where sustained winds of 35 kt were observed, with gusts to 45 knots. The front will weaken from current levels as it moves across Kauai today, then stall and weaken further near Oahu tonight and Friday, bringing a period of showers, and a slight chance of thunderstorms to Kauai waters. Showers associated with the front should soon be evident in radar data from Kauai. A brief period of strong to near-gale N winds will follow the passage of the front, mainly over Kauai waters, where a Small Craft Advisory (SCA) is in effect.
High pressure building N of the area will produce fresh to locally strong NE winds to the W of the stalled front on Friday, mainly over waters W of Oahu. Gentle E to SE winds will persist over waters around Maui and Hawaii Counties. 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 N of the area will lead to an increasing ENE trade wind flow Sunday and Monday.
Significant wave heights at buoys 51001/51101 have been a steady 9-11 feet at 12 seconds for the past 24 hours or more, primarily due to NW swell. This stream of relatively short-period (12-14 seconds) NW swell will continue to move through island waters over the next several days, keeping surf elevated along exposed N and W facing shores, but likely just below High Surf Advisory (HSA) level heights at its peak on Friday. Increased wave heights at these buoys today will likely be due to shorter-period (less than 8-10 seconds) wind chop that will likely not result in significant increases in surf height. A fresh pulse of medium-period NNW swell may arrive on Saturday, with another pulse possible on Monday.
Elsewhere, a small S swell will continue to diminish today. Another long-period S swell is expected by this weekend.

Fire weather

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

HFO Watches/Warnings/Advisories

Small Craft Advisory from 10 AM this morning to 6 PM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel.
Small Craft Advisory from 6 PM this evening to 6 PM HST Friday for Oahu Windward Waters.

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Data Courtesy of NOAA.gov