Hilo

Tonight: Mostly cloudy with isolated showers. Lows 57 to 65 near the shore to 45 to 52 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 73 to 79 near the shore to 61 to 67 at 4000 feet. North winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tuesday Night: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 56 to 65 near the shore to 46 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Kona

Tonight: Partly cloudy. Lows around 68 near the shore to 40 to 47 near 5000 feet. Light winds.

Tuesday: Sunny. Isolated showers in the afternoon. Highs 78 to 83 near the shore to around 64 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Lows around 67 near the shore to 40 to 47 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy with isolated showers. Lows 57 to 67 near the shore to 49 to 56 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 75 near the shore to 66 to 74 near 3000 feet. East winds up to 10 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Lows 57 to 66 near the shore to 49 to 56 near 3000 feet. Southwest winds up to 10 mph.

Kohala

Tonight: Partly cloudy with isolated showers. Lows 57 to 67 near the shore to 49 to 56 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 75 near the shore to 66 to 74 near 3000 feet. East winds up to 10 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Lows 57 to 66 near the shore to 49 to 56 near 3000 feet. Southwest winds up to 10 mph.

South Big Island

Tonight: Mostly clear. Lows around 69 near the shore to around 48 near 5000 feet. East winds up to 15 mph in the evening becoming light.

Tuesday: Sunny. Isolated showers in the afternoon. Highs around 80 near the shore to around 63 near 5000 feet. Light winds becoming southwest around 10 mph in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Lows around 68 near the shore to around 47 near 5000 feet. Light winds becoming southeast up to 10 mph after midnight.

Puna

Tonight: Mostly cloudy with isolated showers. Lows 57 to 65 near the shore to 45 to 52 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 73 to 79 near the shore to 61 to 67 at 4000 feet. North winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tuesday Night: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 56 to 65 near the shore to 46 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Waikoloa

Tonight: Mostly clear. Lows 65 to 71 near the shore to 44 to 49 above 4000 feet. East winds up to 15 mph.

Tuesday: Sunny. Isolated showers in the afternoon. Highs 79 to 84 near the shore to 62 to 67 above 4000 feet. Southeast winds up to 15 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly clear. Lows 65 to 71 near the shore to 44 to 49 above 4000 feet. Light winds becoming south up to 10 mph after midnight.

Detailed Forecast

Synopsis

Generally benign weather prevails through the forecast period. A cold front will bring a brief round of showers and perhaps an isolated thunderstorm Wednesday into Thursday. This will be followed by a reinforcing shot of cool weather.

Discussion

Baroclinic leafing evident on regional satellite along the 30th parallel, a response to digging shortwave energy within NW flow aloft. This will in turn result in cyclogenesis along the attendant cold front north of the islands late Tuesday. The nascent low will quickly strengthen and occlude as it lifts northward away from the area. Associated pressure falls will eradicate the local surface pressure gradient on Tuesday leading to expanding sea breezes during the afternoon followed by stable land breezes overnight. Nothing more than a few interior clouds and isolated showers expected Tuesday afternoon.
As the low lifts north, shortwave energy aloft will pivot through the forecast area driving the cold front eastward through Kauai and Oahu on Wednesday and into the eastern end of the state on Wednesday night. This scenario won't be dissimilar to the most recent frontal passage which brought a brief round of rain followed by dewpoints falling into the upper 50s. Forcing aloft will be stronger this time, so slightly deeper moisture along the front may allow for a better coverage of showers. Mid-level lapse rates are adequate for an isolated thunderstorm or two along the front, but hardly impressive. Combined with low density CAPE profiles, it appears the chance for thunder will be fleeting over the islands themselves, the greater probabilities residing over the waters north and east of the area.
Frontal passage on Wednesday will therefore be accompanied by a transient period of light to moderate showers and just a slight chance of thunder followed by a transition to moderate NW winds and dewpoints falling further into the 50s. Wednesday night through Friday night will feature rather cool weather characterized by large diurnal swings in temperature with typical daytime highs followed by overnight lows falling into the 50s in some locales, particularly sheltered and interior zones.
There remains enough uncertainty in the position of the aforementioned low that post-frontal low-level moist cyclonic flow could impinge on Kauai on Thursday bringing shallow showers to north and west facing facing slopes on Thursday. Primary uncertainty this forecast package is extent of eastward progress of the front and whether the incoming cool/low dewpoint airmass will penetrate as far east as the Big Island. At this time, model consensus suggests forward progress of the front stalls over or immediately east of the Big Island suggesting they are still in the game for a brief period of cooler weather. Dewpoints then rebound into the 60s as trades return for the weekend.

Aviation

Moderate trades will continue through the afternoon, then weaken overnight into tomorrow as a cold front approaches from the northwest. Despite a minor uptick in low level moisture bringing some low level clouds and brief showers to windward areas this afternoon, VFR conditions should generally prevail across the state over the next 24 hours. The lighter flow will give way to sea breezes tomorrow, with clouds and a few showers forming over island interiors by the afternoon.
No AIRMETs are in effect or expected thro

Marine

Trade winds will decline through Tuesday, followed by the passage of a front passage Wednesday and Thursday. Trades will diminish as a surface ridge to the north is weakened and pushed southward, and winds will become light and variable when the ridge moves over the islands Tuesday afternoon. A front will move down the island chain Wednesday and Thursday, bringing a period of rainfall and possible thunderstorms and ushering in moderate to fresh northwest winds. A brief period of fresh prefrontal southwest winds is excepted on Wednesday, mainly over the eastern half of the island chain, but winds are expected to remain below Small Craft Advisory (SCA) strength. Winds will diminish on Thursday on Friday as the front stalls then dissipates near the Big Island. A brief return of trade winds is due on Saturday.
The current northwest swell will gradually decline over the next 24 hours, and forerunners of another northwest swell will arrive late Tuesday. This swell will slowly build through Wednesday and peak Wednesday night and Thursday, leading to High Surf Advisory (HSA) conditions across most north and west facing shores from Kauai to Maui and SCA level seas over exposed waters. As this swell declines late Thursday and Friday, a storm low centered 600 to 700 nm north of Hawaii will send a medium period north swell that could produce HSA surf for north shores. The north swell will lower through the weekend and may be followed by a moderate to large northwest swell on next Monday.
East shore surf surf will decline overnight as trades diminish, though a small pulse of short period northeast swell will be possible Tuesday and Wednesday. Aside from areas exposed to wrapping north swell Thursday into the weekend, east shore surf will be small. The recent out of season south swell will fade by tomorrow, bringing back typical wintertime conditions for south shores. A tiny pulse of south-southwest swell is possible for the weekend.

Fire weather

Winds are forecast to remain below the threshold value while a reinforcing shot of dry air causes afternoon RH values to fall to near or slightly below 40 percent Thursday and Friday. Critical fire weather concerns are not anticipated during the forecast period.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov