West Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 86 near the shore to around 72 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to around 60 above 3000 feet. Northeast winds 10 to 15 mph shifting to the east after midnight. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 82 to 87 near the shore to around 72 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 85. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 71. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 77 to 86. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 68 to 78 in the valleys to around 61 above 4000 feet. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 62 to 68 in the valleys to around 57 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 70 to 79 in the valleys to around 62 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 72 to 84. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 73 to 85. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 69 to 81. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 70 to 83. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A cold front over Maui County will move south through Big Island today, bringing an increase in showers, especially along windward slopes. Breezy east- northeasterly trades will fill in behind the front and persist through much of next week, becoming even stronger by mid- week as strong high pressure builds north of the islands. Typical windward and mauka showers will prevail under the trade flow, with generally drier conditions leeward.

Discussion

A weakening cold front is currently moving through Maui County with the leading edge pushing south toward North Kohala District of the Big Island early this morning. Radar and satellite shows clouds and light to brief moderate showers mainly focused along windward and mauka regions with some showers showers spilling over to leeward locations of the smaller islands. Overnight rainfall totals range from .20 to 2.78 inches with higher totals mainly along windward and mauka locations. Breezy northeast winds have filled in along and behind the front based on latest ASCAT and hourly observations.
The front is forecast to move through north Big Island this morning before becoming more diffused and pushing south through the rest of the island later this afternoon into evening hours. Expect light and variable winds ahead of the front, shifting to breezy east- northeasterly trades in its wake. Mid- level ridging in place over the region will continue to limit vertical development, keeping rainfall rates modest overall.
Following the front, breezy east-northeasterly trades will become established across the state as high pressure builds to the north. Drier more stable air will fill in first for the western end of the state today then for the eastern half of the state later tonight and Monday. During this time dewpoints will drop to the mid to low 60s allowing temperatures to feel a little cooler than normal and should hold into Wednesday. Another reinforcing front with an even stronger high pressure system will arrive midweek, providing another boost in the east- northeasterly trades. With mid level ridging persisting over the region, inversion heights will remain low, keeping the moisture confined to lower levels and focusing clouds and showers over primarily windward and mauka areas. Dewpoints will rebound into the 70's during the second half of the week.

Aviation

A cold front is moving through Maui County and will be moving through Big Island this morning through this afternoon with breezy NE winds filling in behind the front. VFR conditions will prevail behind the front, but MVFR conditions are expected during frontal passage and CLD and SHRA focus mainly along windward and mauka regions. Breezy trades are expected to strengthen out of the NE after the front moves across the state over the next couple of days.
AIRMET Sierra is in effect for Oahu Molokai and Maui windward areas for MTN obscurations due to CLD and SHRA from the front. This is expected to be adjusted to include windward Big Island due to CLD and SHRA. Other areas may be dropped from SIERRA as conditions settle behind the front.
AIRMET Tango is in effect for low-level turbulence over Kauai Oahu Molokai and Maui, and will likely be expanded across the entire state today as winds strengthen behind the frontal passage.

Marine

Rough marine conditions expected through much of the week due to strong trade winds and a series of north to northeast swells. A cold front currently pushing across Maui will continue southeastward and move over the Big Island later today and into tonight. Strong northeast winds will follow in its wake with a quick rise in seas. A Small Craft Advisory remains in effect for many coastal areas today and has been expanded in coverage to include all of the Hawaiian coastal waters starting this evening as the front makes its way through the island chain. Strong northeast winds will persist through much of the week with an uptick expected midweek as the high strengthens and builds north of the area Wednesday into Thursday, bringing the possibility of gales for some of our typical windy channels around Maui County and the Big Island.
A moderate, short-medium period, north-northwest to north swell arrived overnight and will produce elevated surf along north facing shores as it continues to fill in through the day today. With the offshore buoys northwest of the state peaking with energy mostly in the 10 to 12 second energy bands yesterday afternoon and evening, we are expecting near borderline advisory level surf along north facing shores today. Will continue to monitor to see if a High Surf Advisory (HSA) is needed later this morning, as this swell energy is continuing to rise at the Waimea buoy.
A larger moderate period north to north- northeast (010-030 degree) swell will fill in tonight into Monday which should exceed advisory thresholds along north and east facing shores. Due to the northerly direction, areas such as west Maui will also see elevated surf as well as some of the exposed areas of west Big Island near Kua Bay. Another reinforcing northeast swell is expected towards the middle of the week as a gale force low develops northeast of the state on Monday. The combination of these swells will likely produce moderate to heavy surges in north facing harbors such as Kahului and Hilo harbors throughout the first half of the week.
A small, long period, south-southwest swell will keep surf heights near seasonal averages along south facing shores today. THen a pair of south to south-southwest swells should bring above average surf throughout the first half of the week.
Peak monthly tides combined with water levels that are running higher than predicted will lead to minor flooding along the shoreline and in low-lying coastal areas during the morning high tide. A Coastal Flood Statement remains in effect through noon today.

Fire weather

Critical fire weather conditions are not expected through the next few days. Breezy trades will fill in across the state today, but lingering moisture will prevent critical fire weather concerns. Breezy trades are forecast to become even stronger by mid-week, but low- level moisture embedded within the trades will help keep relative humidity from reaching critical thresholds.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel.
Small Craft Advisory from 6 PM this evening to 6 PM HST Monday for Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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