Hilo

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 59 to 67 near the shore to 47 to 54 at 4000 feet. South winds up to 10 mph shifting to the southwest after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 82 near the shore to 63 to 69 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows 60 to 67 near the shore to 48 to 55 at 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Kona

Tonight: Partly cloudy with isolated showers. Lows around 69 near the shore to 43 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 85 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 40 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 69 near the shore to 43 to 50 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy with isolated showers. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. Southeast winds up to 15 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 78 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Lows 60 to 68 near the shore to 51 to 59 near 3000 feet. Southeast winds up to 15 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 78 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

South Big Island

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 70 near the shore to around 48 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows around 70 near the shore to around 49 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 59 to 67 near the shore to 47 to 54 at 4000 feet. South winds up to 10 mph shifting to the southwest after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 82 near the shore to 63 to 69 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows 60 to 67 near the shore to 48 to 55 at 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Waikoloa

Tonight: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to 46 to 52 above 4000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs around 83 near the shore to 63 to 69 above 4000 feet. South winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to 46 to 52 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A relatively dry and stable airmass will persist through midweek. Light to moderate east to southeast winds will hold through mid week ahead of an approaching front. Sea breezes developing during the day should allow for afternoon clouds and light showers over interior and leeward areas. Land breezes should help to clear out leeward and interior areas each night. Chances of rainfall should increase late in the week mainly over Kauai as the tail end of a front stalls near Kauai on Friday. More unsettled weather is possible this weekend into early next week as another front approaches the state.

Discussion

A ridge of high pressure just north of the state will continue to produce stable and mostly dry conditions with light to moderate east to southeast winds through the middle of the week. Rainfall totals over the past 12 hours have been nearly nonexistent. Under this east to southeast flow, the main areas for any passing showers will likely be east Maui or southeast Big Island, although rain amounts should be light due to this stable pattern. Winds will be light enough for sea breezes to develop each day, which will allow for afternoon clouds and maybe a light shower or two during the afternoons over interior and leeward areas. Land breezes developing at night should allow for mostly clear mornings across many areas.
Starting Thursday, a front approaching the state will cause the low level flow to become more southerly ahead of the front. Latest deterministic models and ensemble guidance is now in better agreement with the front stalling near Kauai on Friday. Rainfall chances will generally increase on Friday mainly over Kauai, but the amount rainfall will depend on where the front ends up stalling. With precipitable water values increase to around 1.7 inches based on the latest GFS model, there definitely will be potential for heavy showers on Kauai on Friday. At this time instability does look limited, so the threat for thunderstorms looks to be low.
By Saturday, the front or what is remaining of the front should lift northward with improving weather conditions over Kauai. That being said, long range guidance is in fairly good agreement with a stronger front approaching the state on Sunday. So although details remain uncertain, confidence is increasing for some unsettled weather this weekend into early next week.

Aviation

Light to moderate ESE low-level flow will persist, with VFR conditions prevailing. The best chance for clouds and brief showers will be over interior and leeward sections through the late afternoon hours, then over windward and mauka locations late tonight through early Tuesday.
AIRMETs are not anticipated through the 24-h period.

Marine

Weak surface ridging north of the islands will steer light to moderate ESE winds through Wednesday before turning southerly Thursday as a front approaches from the northwest and passes through portions of the western end of the state Thursday into Friday.
The nearshore Hanalei PacIOOS buoy suggests surf remains just shy of the High Surf Advisory (HSA) threshold this afternoon with slightly decreased values at Waimea owing to shadowing by Kauai. However, favored NW-facing exposures on Oahu likely remain near the HSA threshold as well. This moderate, long period NW (310) swell will subside through the first half of the night as long period forerunners of the next swell in the sequence arrive. Tuesday will feature building large, long period surf that will easily exceed HSA thresholds for N and W facing exposures, potentially including Leeward Big Island. West-facing shores of Leeward Big Island potentially reach their warning threshold late Tuesday into Tuesday night. A reinforcing pulse of similar size will help keep surf at advisory levels through Wednesday before dropping below advisory thresholds Thursday. A High Surf Advisory has therefore been issued for susceptible shorelines of Kauai through Maui. A large, long period NW (320) swell will generate surf to High Surf Warning thresholds along N and W facing shores Friday, peak Saturday then slowly subside into early next week.
Surf along E and S facing shores remains small through the period.

HFO Watches/Warnings/Advisories

High Surf Advisory from 6 AM Tuesday to 6 AM HST Thursday for Niihau, Kauai Leeward, Oahu North Shore, Waianae Mountains, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.

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Data Courtesy of NOAA.gov