Hilo

Tonight: Mostly cloudy with scattered showers. Lows 59 to 67 near the shore to 48 to 54 at 4000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers. Highs around 80 near the shore to 65 to 70 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 61 to 69 near the shore to 51 to 57 at 4000 feet. Light winds. Chance of rain 40 percent.

Kona

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 70 near the shore to 44 to 50 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 82 to 87 near the shore to around 68 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers after midnight. Lows around 71 near the shore to 45 to 51 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 60 to 68 near the shore to 51 to 58 near 3000 feet. East winds up to 15 mph in the evening becoming light. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs around 79 near the shore to 69 to 78 near 3000 feet. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 62 to 70 near the shore to 53 to 60 near 3000 feet. Light winds. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 60 to 68 near the shore to 51 to 58 near 3000 feet. East winds up to 15 mph in the evening becoming light. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs around 79 near the shore to 69 to 78 near 3000 feet. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 62 to 70 near the shore to 53 to 60 near 3000 feet. Light winds. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 72 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs around 84 near the shore to around 68 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows around 73 near the shore to around 51 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 59 to 67 near the shore to 48 to 54 at 4000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Monday: Partly sunny with scattered showers. Highs around 80 near the shore to 65 to 70 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 61 to 69 near the shore to 51 to 57 at 4000 feet. Light winds. Chance of rain 40 percent.

Waikoloa

Tonight: Partly cloudy. Isolated showers in the evening. Lows 67 to 73 near the shore to 46 to 52 above 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 82 to 87 near the shore to 65 to 71 above 4000 feet. Northeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy. Lows 69 to 74 near the shore to 48 to 53 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

High pressure north of Hawaii will keep moderate to locally breezy trade winds and scattered windward and mauka showers going through tonight. Light winds then develop Monday through Wednesday as a surface ridge moves across the state and weakens the pressure gradient. This will allow local daytime sea breezes and nighttime land breezes to develop across the islands. A weak front is expected to move across the state on Thursday. Light to moderate northeast to east trade winds and scattered windward and mauka showers return by next weekend.

Discussion

Surface high pressure far north and northeast of the state will keep moderate to locally breezy trade winds through tonight. Satellite and radar imagery continue to show some enhanced windward shower activity this afternoon as an upper-level trough passes by to our north. Expect trade winds to start to weaken tonight as the surface high drifts east. However, will continue to see enhanced windward and mauka showers due to the proximity of the upper-level trough.
Light and variable winds are then expected to develop across the state Monday through Wednesday as a surface ridge moves across the region and a cold front approaches the state from the northwest. As the pressure gradient weakens the lighter winds will allow for the development of local daytime sea breezes, with isolated leeward and interior showers, and nighttime land breezes. These afternoon sea breezes could bring some much need moisture to the drier leeward portions of the islands.
Guidance continues to show a weak cold front moving across the islands on Thursday. Light to occasionally moderate showers associated with this front are expected to be brief as it quickly moves across the state and dissipates Thursday night into Friday. We don't expect any significant rainfall later this week.
Winds look to then strengthen a bit out of the north behind the front and become northeasterly by Friday. Light to moderate northeast to east trade winds look to return by next weekend bringing the return of scattered windward and mauka showers

Aviation

An upper level trough over the eastern part of the state will produce moderate turbulence between FL300 and FL400. AIRMET Tango is posted for the entire state and is forecast to shift east of the area tonight. Low level winds will be weakening and veering southeast tonight, becoming light and variable Monday.
VFR conditions prevail tonight with no other AIRMETs expected.

Marine

Trade winds will steadily decline tonight and will be suppressed through much of the coming week. Offshore buoys and coastal wind observations show that the trades have already begun to decline as surface high pressure centered about 650 nm northeast of the Hawaii moves rapidly eastward, and the Small Craft Advisory (SCA) for the typically windy waters around the Big Island and Maui County through has been cancelled. A surface ridge trailing the high will move southward tonight and Monday, causing the declining winds to shift southeasterly over all waters by late tonight and eventually southerly around Kauai on Monday. The ridge will settle over the central portion of the island chain and produce light to gentle and variable winds Tuesday and Wednesday. A weak front is expected move over the area on Thursday and bring gentle to locally moderate northerly winds. A weak surface high passing near or just north of Kauai may generate a brief period of gentle trades on Thursday night and Friday.
Surf along north and west shores will be at a minimum during the during the next 24 hours, followed by a significant rise for much of the coming week. The current northwest swell of 2 to 3 feet at 12 to 13 seconds should be reinforced by a moderate pulse of north-northwest swell that will arrive late Monday and peak on Tuesday. A very intense storm developed between Japan and the Aleutian islands yesterday, and a series of additional storms is expected to form in a similar area every two to three days during the next week. The first of several large long-period northwest swells will build through the day on Tuesday and will produce surf well above High Surf Advisory levels by Tuesday night and Wednesday. Surf will likely exceed High Surf Warning levels Thursday into next weekend if conditions evolve as projected. Seas should also surpass the SCA threshold of 10 feet for waters exposed to the large swells.
Mainly small surf is due elsewhere. East shore surf is already below December average. As trades decline overnight then become disrupted, east shore surf will be small through much of the week, aside from some wrap from larger northwest swell Wednesday into next weekend. Surf along south facing shores will seasonally small, mainly due to short-period southeast swell.
Peak monthly tides combined with water levels running higher than predicted could lead to minor coastal flooding issues for vulnerable low-lying coastal areas tonight. Impacts will be confined to the early morning high tides between midnight and daybreak. Conditions peaked with the full moon last night and will be borderline during the high tide cycle early Tuesday morning.

Fire weather

No critical fire weather conditions expected through the upcoming weekend. Conditions will remain relatively dry through Wednesday. A weak cold front may bring an uptick in showers later this week. Moderate to locally breezy trade winds today will give way to light and variable winds Monday through Wednesday, with light to moderate trade winds returning by next weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov