West Kaua’i

Today: Mostly cloudy with frequent showers and slight chance of thunderstorms until late afternoon, then mostly sunny with slight chance of thunderstorms and isolated showers late in the afternoon. Locally heavy rainfall possible. Highs around 80 near the shore to around 69 above 3000 feet. Northwest winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly clear. Slight chance of thunderstorms and isolated showers early in the evening. Locally heavy rainfall possible early in the evening. Lows around 66 near the shore to around 56 above 3000 feet. North winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Sunny with isolated showers. Highs around 81 near the shore to around 71 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Today: Cloudy with frequent showers and slight chance of thunderstorms until late afternoon, then partly sunny with scattered showers and slight chance of thunderstorms late in the afternoon. Locally heavy rainfall possible. Highs 77 to 83. West winds up to 10 mph. Chance of rain 90 percent.

Tonight: Partly cloudy. Scattered showers and slight chance of thunderstorms early in the evening, then isolated showers in the late evening and early morning. Locally heavy rainfall possible early in the evening. Lows around 66. Light winds. Chance of rain 30 percent.

Saturday: Sunny with isolated showers. Highs 78 to 83. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Today: Cloudy with frequent showers and slight chance of thunderstorms until late afternoon, then partly sunny with scattered showers and slight chance of thunderstorms late in the afternoon. Locally heavy rainfall possible. Highs 72 to 77 in the valleys to around 63 above 4000 feet. West winds up to 15 mph. Chance of rain 90 percent.

Tonight: Partly cloudy. Scattered showers and slight chance of thunderstorms early in the evening, then isolated showers in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows 58 to 65 in the valleys to around 55 above 4000 feet. Light winds. Chance of rain 40 percent.

Saturday: Mostly sunny. Isolated showers until late afternoon, then scattered showers late in the afternoon. Highs 71 to 78 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 30 percent.

North Kaua’i

Today: Mostly cloudy with frequent showers and slight chance of thunderstorms until late afternoon, then mostly sunny with slight chance of thunderstorms and isolated showers late in the afternoon. Locally heavy rainfall possible. Highs 71 to 79. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 90 percent.

Tonight: Mostly clear. Slight chance of thunderstorms and isolated showers early in the evening. Locally heavy rainfall possible early in the evening. Lows 60 to 68. West winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Sunny with isolated showers. Highs 73 to 80. Light winds. Chance of rain 20 percent.

East Kaua’i

Today: Cloudy with frequent showers and slight chance of thunderstorms until late afternoon, then partly sunny with scattered showers and slight chance of thunderstorms late in the afternoon. Locally heavy rainfall possible. Highs 71 to 81. Southwest winds up to 10 mph shifting to the north in the afternoon. Chance of rain 90 percent.

Tonight: Partly cloudy. Scattered showers and slight chance of thunderstorms early in the evening, then isolated showers in the late evening and overnight. Locally heavy rainfall possible early in the evening. Lows 60 to 70. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Saturday: Mostly sunny with isolated showers. Highs 72 to 82. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A low northwest of the state will swing east before lifting north today and be absorbed is a stronger, nearly stationary, low far northwest of the state. A front just west of Kauai associated with the low will move eastward pushing a broad band of showers eastward across the state through the day. Strong southerly winds ahead of the front will shift over Oahu this morning with light westerly winds filling in behind the front. Drier and lighter winds are expected to fill in across the state Saturday as the front pushes east of the state and weakens. Chance of showers will increase again across the state Sunday into early next week. Land/seabreezes will dominate much of the weather pattern next week as the low remains north of the state.

Discussion

Latest satellite imagery shows a low 500 sm northwest of Kauai early this morning with south to north orientated front just west of Kauai. A broad cloud shield remains over the the state. Radar light to moderate showers blanketed across the state with heavier showers building over Kauai early this morning. High resolution model guidance shows the frontal band moving east across the state today shifting the chances of heavier showers across Oahu later this morning and afternoon before moving onwards to Maui County tonight. Steady light to moderate showers will continue along the southeast Big Island. Thus the Flood Watch remains in effect for the state through this afternoon. The High Wind Warning (HWW) for windier areas of Kauai has been canceled as southerly winds eased and shifted more westerly. Strong southerly winds remain over Oahu which could still produce downsloping winds in areas north and downwind of steep terrain. However, the HWW for these winder areas has been downgraded to a Wind Advisory as overall wind speeds have weakened. As the front progresses towards the central island later this afternoon and evening wind speeds will continue to trend downward. Behind the front winds will ease to light and variable speeds. Big Island summits will continue to see advisory level winds through today before tapering off this afternoon thus the Wind Advisory remains in effect through this afternoon. The Winter Weather Advisory also remains in effect through this afternoon.
The low will become absorbed in a stronger, nearly stationary, low far northwest of the state Saturday. Remnant moisture lingering over the eastern half of the state will still produce some scattered showers but overall flooding threat will have decreased as low to mid level drier air filters in from the west to east across the state. An upper level shortwave is expected to dip southeastward Sunday, likely supporting another active weather period across the state that may extend through early next week. Winds will remain light through much of next week as this larger low slowly weakens through the first half of next week before shift northeast during the second half of next week. Light winds and lingering moisture will allow for afternoon sea breezes building clouds and increase showers over interior areas. Land breezes will develop overnight providing some clearing. This pattern is expected to persist through much of next week as this low keeps the island chain cut off from tradewinds returning.

Aviation

The threat of heavy rainfall will persist across the state today, which could lead to periods of MVFR to IFR VSBYS/CIGS along with gusty southerly winds. Conditions should gradually begin to improve over the western end of the state later today through tonight.
AIRMET Sierra is in effect for mountain obscuration above 020 ft for Kauai and Oahu. This will likely need to be expanded down the island chain later this morning, as showers expand eastward down the island chain.
AIRMET Tango remains in effect for moderate turbulence between FL180 and FL360 across the entire islands, and for moderate turbulence downwind of terrain for Oahu and Kauai.
AIRMET Zulu remains in effect for moderate icing between 140-FL200.

Marine

As the low pressure system to the northwest further deepens, we will likely see a few strong to severe thunderstorms capable of producing waterspouts and damaging winds over the coastal waters. Rough boating conditions are expected with elevated seas and strong to near gale force southerly winds. As such a Small Craft Advisory is in effect for all waters through at least 6PM.
Strong southerly winds are expected to slowly decrease west to east today. Surf along the southern shores is slowly declining. The High Surf Advisory has been cancelled as surf has fallen below criteria.
Along north facing shores, the current northwest (320 degree) swell is slowly decreasing and should dissipate to background levels on today. However a smaller short-period northwest swell generated by the aforementioned low will fill in tonight through early next week.
Surf along east facing shores could see an increase later this week due to the strengthening southeasterly winds especially for southeast exposures.

HFO Watches/Warnings/Advisories

Flood Watch through this afternoon for all Hawaii islands,
Wind Advisory until 6 PM HST this evening for Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Big Island Summits, Koolau Windward, Koolau Leeward.
Winter Weather Advisory until 6 PM HST this evening for Big Island Summits.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters,

Data Courtesy of NOAA.gov