Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs around 83 near the shore to around 71 above 3000 feet. West winds up to 15 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 70 near the shore to around 58 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Friday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to around 72 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with scattered showers and isolated thunderstorms. Highs 77 to 84. Southwest winds up to 15 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 68. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 84. Northeast winds 20 to 25 mph decreasing to 10 to 25 mph in the afternoon. Chance of rain 70 percent.

Kaua’i Mountains

Today: Frequent showers and isolated thunderstorms. Highs 70 to 79 in the valleys to around 62 above 4000 feet. Light winds becoming north up to 15 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Breezy. Frequent showers. Lows 59 to 67 in the valleys to around 56 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain near 100 percent.

Friday: Cloudy and breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 70 to 79 in the valleys to around 62 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 90 percent.

North Kaua’i

Today: Breezy. Scattered showers and isolated thunderstorms in the morning, then frequent showers and isolated thunderstorms in the afternoon. Highs 73 to 83. Southwest winds up to 10 mph shifting to the north up to 20 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Breezy. Frequent showers in the evening, then numerous showers after midnight. Lows 61 to 69. Northeast winds 10 to 25 mph. Chance of rain 90 percent.

Friday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 84. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

East Kaua’i

Today: Breezy. Frequent showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Highs 70 to 83. Southwest winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain near 100 percent.

Tonight: Breezy. Frequent showers in the evening, then numerous showers after midnight. Lows 62 to 72. Northeast winds 10 to 20 mph. Chance of rain near 100 percent.

Friday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 69 to 81. Northeast winds 10 to 20 mph. Chance of rain 70 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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