Hilo

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows around 62 near the shore to around 48 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs around 78 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Kona

Today: Mostly sunny. Isolated showers in the afternoon. Highs 79 to 84 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 64 near the shore to around 49 near 5000 feet. Light winds.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 77 to 82 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Waimea

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 78 near the shore to 70 to 77 near 3000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 61 near the shore to 47 to 55 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Kohala

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 78 near the shore to 70 to 77 near 3000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 61 near the shore to 47 to 55 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

South Big Island

Today: Sunny. Highs around 82 near the shore to around 71 near 5000 feet. Southeast winds up to 10 mph.

Tonight: Mostly clear. Lows around 64 near the shore to around 48 near 5000 feet. Light winds.

Monday: Sunny. Isolated showers in the afternoon. Highs around 80 near the shore to around 69 near 5000 feet. Light winds becoming south up to 10 mph in the afternoon. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows around 62 near the shore to around 48 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs around 78 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Waikoloa

Today: Sunny and breezy. Highs around 81 near the shore to 65 to 72 above 4000 feet. Northeast winds up to 20 mph.

Tonight: Mostly clear. Breezy. Lows around 65 near the shore to 44 to 52 above 4000 feet. Southeast winds up to 20 mph.

Monday: Sunny. Highs around 79 near the shore to 63 to 70 above 4000 feet. Northeast winds up to 15 mph.

Detailed Forecast

Synopsis

A high pressure system passing from west to east just north of the region will keep moderate to locally breezy trade winds in the forecast this weekend. An upper level ridge over the state will keep fairly stable weather conditions in the forecast for most areas through Monday. A low level trough moving in from the east will increase shower trends for the windward Big Island and Maui on Tuesday. Another high pressure system passing by north of the islands on Wednesday and Thursday will keep moderate trade winds blowing with brief showers possible, favoring windward and mountain areas in a fairly stable trade wind regime.

Discussion

The satellite imagery this morning shows cloud bands associated with an old frontal boundary drifting into the northwestern islands on the moderate to locally breezy trade winds. A high pressure system is passing by just north of the region. A cold front currently located far northwest of the state will stall north of the island chain on Wednesday with no weather impacts expected with this system.
In the short term forecast, the lingering clouds north of the state from an old dissipated cold front will produce brief showers drifting in on the trade winds over Kauai and Oahu today. These showers will mainly affect windward and mountain areas of both islands.
Otherwise fairly stable weather trends are expected through the week in a continued moderate to locally breezy trade wind weather pattern. An upper level ridge over the islands will keep trade wind inversion heights on the low side around 4000 to 7000 feet through Monday. This inversion will tend to cap vertical cloud heights and decrease shower activity.
A low level trough will drift into the eastern islands on Tuesday and Wednesday, increasing inversion heights and shower activity across the state, with highest shower coverage forecast along the windward slopes of the Big Island and east Maui.
The extended range forecast guidance from Thursday onward continues to show a weak upper low developing just east of the Big Island. This upper low may increase trade wind shower trends on Thursday and Friday across the region. These increasing cloud and shower trends would favor the typical windward and mountain areas.

Aviation

Moderate trade winds will dominate through the forecast period. Patchy broken to overcast low clouds upwind from the state will affect windward portions of the islands today. AIRMET Sierra for Tempo Mountain Obscuration remains in effect across Kauai, and may need to be expanded later today as more areas become affected by the low cloud area.

Marine

Moderate to locally strong trades have returned and will hang around through much of the week. These winds combined with large seas associated with a west-northwest swell moving through have led to Small Craft Advisory conditions for all Hawaiian waters, which will continue through much of the day today before dipping below as the swell moves out. Trades will shift to a more northeast direction tonight through Tuesday as the islands become positioned between a gale passing to the southeast and the ridge to the north.
Surf along exposed north and west facing shores will gradually lower through the day as the west-northwest swell that peaked Saturday begins to move out. Offshore buoy observations this morning extrapolated to the islands support the transition from a warning to an advisory. Expect the advisory-level surf to hold into Monday as a new, long-period west-northwest pulse arrives tonight. Heights will then dip below advisory levels for north and west facing shores Tuesday through midweek.
For the extended, guidance shows a powerful system lifting northeast from Japan to the western Aleutians Monday through Wednesday, with a decent sized area of gale- to hurricane-force winds focused at the islands. Given the distance away from the islands and the quick northeast track, confidence remains low at this time. If it does materialize, a long-period, west-northwest swell will be expected by or come Friday, that will linger into next weekend.
Surf along east facing shores will rise today in response to an easterly swell arriving from a gale positioned around 650 NM east of Hilo. Morning observations at the Hilo buoy reflect this and have picked up within the 8-12 second bands. Guidance has this easterly swell lingering through Monday before easing into midweek.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for north and west facing shores of Niihau, Kauai, Oahu and Molokai, including north facing shores of Maui and west facing shores of the Big Island.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters.
Small Craft Advisory until 6 PM HST Monday for windier waters and channels around Maui and the Big Island.

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Data Courtesy of NOAA.gov