Hilo

Today: Partly sunny with scattered showers. Highs 79 to 87 near the shore to around 69 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 54 to 59 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 79 to 87 near the shore to around 70 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 89 near the shore to 65 to 70 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 73 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 89 near the shore to 65 to 70 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Waimea

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 64 to 85. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 63 to 72 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 64 to 84. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 64 to 85. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 63 to 72 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 64 to 84. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 68 near 5000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Breezy. Lows around 74 near the shore to around 52 near 5000 feet. Northeast winds up to 20 mph becoming 10 to 15 mph after midnight.

Monday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 87 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs 79 to 87 near the shore to around 69 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 54 to 59 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 79 to 87 near the shore to around 70 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Sunny and breezy. Isolated showers in the afternoon. Highs 84 to 89 near the shore to 65 to 73 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 74 near the shore to 50 to 55 above 4000 feet. Southeast winds up to 15 mph.

Monday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 84 to 90 near the shore to 65 to 73 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds will gradually strengthen over the next couple of days as a stable pattern of mainly windward showers prevails. A batch of moisture moving in the trade wind flow will produce an increase in showers Monday night and Tuesday. Trade winds are expected to strengthen Wednesday and Thursday, bringing drier weather.

Discussion

A stable, moderate to locally breezy trade wind flow will prevail through tomorrow. A rather strong 1033 mb high is sitting about 1300 miles north of the state. A trough south of the high is keeping the pressure gradient and associated trade winds slightly weaker than would be expected with a high of this strength. As the trough fills, trade winds will gradually strengthen. A mid- level ridge over the islands will maintain stable conditions, and as a shallow batch of moisture moves westward today, drier air will slowly move over the region from the east. Modest rainfall will be focused over windward slopes, and mostly dry conditions are expected leeward. Exceptions will be on the Kona slopes of the Big Island, where clouds and showers will develop each afternoon, and leeward Kauai, which could see a couple of brief showers this afternoon.
An increase in shower activity is due Monday night and Tuesday as another batch of moisture moves in on the trades. This area will be deeper than the one that passed through yesterday, which suggests that shower chances will be higher, especially for windward areas. Leeward slopes of the Big Island, and possibly Haleakala, will likely be active Tuesday afternoon, while leeward areas elsewhere will experience a few passing showers. A mid-level trough will accompany the moisture, but generally stable conditions will remain aloft, minimizing chances for any heavy rainfall.
Drier conditions and stronger trade winds will develop Wednesday and Thursday as the mid-level trough moves away and the high to the north builds. Expect minimal windward rainfall and dry conditions over most leeward areas.

Aviation

Moderate trades will remain in place through the next few days. Clouds and showers will favor windward and mountain areas and night time hours. In addition, clouds and showers will build up on the Kona slopes of the Big Island each afternoon. A few of the showers could bring brief MVFR conditions. Otherwise, VFR should prevail.
No AIRMETs are currently in effect.

Marine

A strengthening high pressure system far north of the Hawaiian Islands will keep trade winds in the fresh to locally strong range through much of this week. Trade wind speeds will be strong enough to support Small Craft Advisory (SCA) conditions over the windier waters and channels near Maui and the Big Island. The SCA was extended in time for these waters out through Tuesday. Additional waters will likely be added later this week as wind speeds increase.
Background south swell energy pulses are forecast to continue, with surf remaining below average through much of this week. Small, choppy surf will increase along east facing shores as locally strong trade winds increase over the next few days.
Spring tides will peak this afternoon, with local tide gauges showing water levels are still running about a half a foot above guidance and at least 1 foot higher than the Mean Higher High Water (MHHW) threshold at Hilo, Kahului, and Honolulu. The Coastal Flood Statement for isolated minor flooding remains in effect through Monday evening.

Fire weather

A typical summer trade wind weather pattern will prevail into Monday, followed by wetter conditions Monday night and Tuesday. On Wednesday and Thursday, trade winds will strengthen, and somewhat dry and stable conditions will develop. This could lead to some fire weather concerns.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov