Hilo

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 59 to 68 near the shore to 47 to 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 77 to 82 near the shore to around 65 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy with isolated showers. Lows 59 to 68 near the shore to 48 to 55 at 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Kona

Tonight: Mostly clear. Haze. Lows 67 to 72 near the shore to 45 to 50 near 5000 feet. Light winds.

Monday: Sunny and haze. Highs 81 to 86 near the shore to around 65 near 5000 feet. Southwest winds up to 10 mph.

Monday Night: Mostly clear. Haze. Lows 67 to 72 near the shore to 45 to 50 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 68 near the shore to 50 to 58 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 61 to 82. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows 59 to 68 near the shore to 50 to 58 near 3000 feet. East winds 10 to 15 mph.

Kohala

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 68 near the shore to 50 to 58 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 61 to 82. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows 59 to 68 near the shore to 50 to 58 near 3000 feet. East winds 10 to 15 mph.

South Big Island

Tonight: Mostly clear. Haze. Lows around 72 near the shore to around 51 near 5000 feet. Northeast winds up to 15 mph.

Monday: Sunny and haze. Highs around 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph.

Monday Night: Mostly clear. Haze. Lows around 72 near the shore to around 51 near 5000 feet. Northeast winds 10 to 15 mph.

Puna

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 59 to 68 near the shore to 47 to 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 77 to 82 near the shore to around 65 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy with isolated showers. Lows 59 to 68 near the shore to 48 to 55 at 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Waikoloa

Tonight: Mostly clear. Haze. Lows 67 to 73 near the shore to 46 to 52 above 4000 feet. Southeast winds up to 15 mph.

Monday: Sunny…breezy and haze. Highs around 83 near the shore to 63 to 70 above 4000 feet. Northeast winds up to 20 mph.

Monday Night: Mostly clear. Haze. Lows 67 to 72 near the shore to 47 to 52 above 4000 feet. East winds up to 10 mph in the evening becoming light.

Detailed Forecast

Synopsis

Light trades give way to southerly winds during midweek. A cold front will bring a brief round of showers to Kauai through Oahu before stalling just west or possibly over Maui County. The front then dissipates as it lifts north late this week. Winds generally hold out of the south through next weekend.

Discussion

Blocking high pressure anchored over the western Aleutians favors a southward-displaced Pacific jet through the forecast period. This in turn favors a tendency for low pressure to develop near/west of the islands with more frequent opportunities for rainfall. In the near term, light to moderate trades will usher existing moisture west of the islands tonight bringing an end to organized shower activity that has focused over windward and mauka areas today, particularly those of Maui and the Big Island.
Deepening mid-level troughing east of the Dateline then elicits upstream pressure falls that wipe out the local pressure gradient causing light SE/S winds to be variable at times through mid-week. Afternoon sea breezes may have just enough moisture to produce pockets of light showers over island interiors, but generally speaking moisture remains limited and dry mid-level air will provide a firm capping inversion throughout this time. This trough triggers a low amplitude frontal wave north of the islands that helps sweep a shallow cold front into the area that will reach Kauai on Wednesday night and Oahu on Thursday before stalling near or over Maui County. Light southerlies may deliver pockets of leeward showers upon the approach of the front, but the bulk of rainfall will focus windward and mauka, especially over Kauai where the building northerly gradient will be strongest. A very weak gradient over Oahu suggests potential for afternoon sea breezes to capitalize on the frontal moisture band Thursday afternoon. This would favor increased afternoon showers, but the outcome will be very sensitive to strength of modest background winds.
Strong consensus exists among the suite of global models that the Pacific jet will continue to sink southward during the forecast period bringing potential for another frontal passage over the western portion of the state early next week.

Aviation

This afternoon, moisture embedded within moderate trade winds has continued to support low clouds with occasional showers for north through east sections of the islands of Maui County and the Big Island. AIRMET Sierra is in effect for mountain obscuration for these areas, but conditions are expected to improve tonight as an upper trough that is currently over the state moves southeast and drier air settles over the region.
Drier conditions are expected into Monday, with light to moderate background trade wind flow continuing. Winds will weaken further and begin to veer southeasterly on Monday night into Tuesday as a front approaches closer to the islands from the northwest.
AIRMET Tango remains in effect for moderate upper level turbulence across the island chain. This area of turbulence associated with an upper-level jet is expected to move southeast tonight, with moderate turbulence decreasing over the state on Monday.

Marine

An area of high pressure will remain north of the Hawaii region, producing gentle to moderate easterly winds through Monday, then decreasing and veering more southeasterly to southerly Tuesday to Wednesday as another cold front moves into the region from the northwest. This front may move into the western Hawaiian islands late Wednesday into Thursday, then diminish by Friday.
The current medium-period north-northwest (340-350 degree) swell will continue to slowly fade into Monday, bringing surf back down to below average levels for this time of year. The next two long to medium-period overlapping northwest (310-320 degree) swells will arrive on Monday, boosting surf along north and west facing shores and possibly reaching marginal advisory levels by Wednesday.
Choppy east shore surf will remain small, then decline further over the next few days as trades gradually ease. Expect minimal background energy for south facing shores, keeping south shore surf heights just above flat levels.
The peak monthly tides are no longer predicted to cause coastal flooding issues, so the Coastal Flood Statement was cancelled earlier today after the morning high tide cycle.

Fire weather

Conditions remain below critical fire thresholds through the week as winds remain light and RH elevated. Winds further ease as the week progresses, eventually transitioning to southerly.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov