Hilo

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 65 to 73 near the shore to around 58 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 65 to 72 near the shore to around 57 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Kona

Tonight: Partly cloudy. Isolated showers in the evening. Lows 68 to 75 near the shore to around 55 near 5000 feet. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 40 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Lows 67 to 74 near the shore to 51 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 73 near the shore to 57 to 66 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 82 near the shore to 68 to 79 near 3000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 72 near the shore to 56 to 65 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 73 near the shore to 57 to 66 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 82 near the shore to 68 to 79 near 3000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 72 near the shore to 56 to 65 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Lows around 75 near the shore to around 59 near 5000 feet. East winds up to 20 mph.

Monday: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83 near the shore to around 68 near 5000 feet. East winds up to 25 mph. Chance of rain 40 percent.

Monday Night: Partly cloudy. Breezy. Lows around 75 near the shore to around 57 near 5000 feet. East winds up to 20 mph.

Puna

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 65 to 73 near the shore to around 58 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 83 near the shore to 64 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 65 to 72 near the shore to around 57 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear. Breezy. Lows 70 to 75 near the shore to 53 to 59 above 4000 feet. East winds up to 20 mph.

Monday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 83 to 90 near the shore to 67 to 73 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Monday Night: Mostly clear. Lows 69 to 75 near the shore to 52 to 58 above 4000 feet. Northeast winds up to 15 mph shifting to the southeast after midnight.

Detailed Forecast

Synopsis

Breezy trades will continue through Monday, bringing limited showers mainly windward and mauka. An upper level low will help weaken winds and turn them out of the south Wednesday. Showers will increase as moisture increases with the potential for heavy rain across Hawaii.

Discussion

High pressure north of Hawaii and a weak disturbance passing to the south will result in breezy trade winds and stable weather through Monday. Scattered low clouds and isolated showers will move through the trade wind flow and primarily impact windward slopes, but rainfall accumulations will remain light.
Winds will weaken and veer southeasterly by late Tuesday, and south by Wednesday, as a sharp trough approaches from the northwest. A surface low will form along the trough and southerly winds will draw deep tropical moisture over the islands, while a cold pool aloft associated with the upper low will act to destabilize the atmosphere over the state. PW values will increase to around 2 inches and dewpoints will rise to around 70 Thursday and into the lower 70s Friday. As this deeper moisture moves in, heavy rain will become likely. The timing and location of the moisture is depicted slightly different in the long range models, but at this time it appears all the islands will be impacted at some point. Thus, not getting too specific in the forecast details for now, but expect an overall wetter pattern and southerly winds from around late Wednesday through at least Friday, and possibly lingering into next weekend.

Aviation

Moderate trades will continue into Tuesday with isolated showers across windward and mountain areas where short-lived MVFR conditions are possible.
Otherwise, VFR conditions will prevail across the state through Monday.
AIRMET Tango continues for moderate turbulence in downwind mountain areas.

Marine

High pressure north of the Hawaiian Islands will maintain fresh to locally strong trade winds through Monday. The Small Craft Advisory for the windier waters and channels around Maui County and the Big Island remains in effect through Monday afternoon. Thereafter, high pressure to the north weakens and trades will start to diminish. Troughing developing northwest of the islands will likely to cause winds to veer out of the southeast around midweek and bring increased shower activity for the latter half of the week.
A new small, long-period south swell will slowly fill in tonight and Monday, with a peak slightly above average Tuesday into Wednesday. Near or slightly below average surf will hold through the rest of the week be maintained by a mix of new, small south swells.
A small, medium-period northwest swell will arrive tonight and peak Monday, producing a small bump in surf through Tuesday. Surf will continue to trend up for north shores as a slightly larger long-period northwest swell peaks Wednesday. Surf may approach moderate levels late in the week as a medium-period northwest swell further increases. Surf along east facing shores will be elevated and choppy through Monday due to the locally strong trades.
A small, long-period west swell originating from Typhoon Choi-wan is forecast to reach the islands Thursday into the weekend, which may produce moderate surf for west-facing shores of the Big Island.

Fire weather

Breezy trades will continue into Tuesday with RH values just above the critical threshold for fire weather each afternoon through Tuesday. Fire weather risk then diminishes through the remainder of the week as moisture increases, winds decrease, and showers increase in coverage. The inversion should range from 6 kft to 8 kft through Monday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov