Photo Credit: Tyler Rooke

West Side

Rest Of Today: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers in the afternoon. Highs 77 to 84. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 69 to 76. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 87. East winds 10 to 25 mph. Chance of rain 40 percent.

South Side

Rest Of Today: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers in the afternoon. Highs around 85. Northwest winds up to 15 mph. Chance of rain 70 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 68 to 77. North winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 88. Northeast winds up to 10 mph increasing to up to 20 mph in the afternoon. Chance of rain 20 percent.

North Shore

Rest Of Today: Breezy. Showers and isolated thunderstorms in the morning, then numerous showers in the afternoon. Highs 78 to 83 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain near 100 percent.

Tonight: Breezy. Scattered showers in the evening, then occasional showers after midnight. Lows around 72 near the shore to around 54 near 5000 feet. Southeast winds 10 to 20 mph. Chance of rain near 100 percent.

Monday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 79 to 84 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

Central Maui

Rest Of Today: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers in the afternoon. Highs 80 to 85. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 68 to 73. East winds up to 15 mph. Chance of rain 20 percent.

Monday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 82 to 88. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

Upcountry

Rest Of Today: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then scattered showers in the afternoon. Highs around 60 at the visitor center to around 63 at the summit. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 49 at the visitor center to around 43 at the summit. Southeast winds up to 20 mph increasing to 10 to 25 mph after midnight. Chance of rain 50 percent.

Monday: Windy. Partly sunny with scattered showers. Highs around 62 at the visitor center to around 66 at the summit. East winds 10 to 30 mph. Chance of rain 50 percent.

East Maui

Rest Of Today: Breezy. Showers and isolated thunderstorms in the morning, then numerous showers in the afternoon. Highs 78 to 83 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain near 100 percent.

Tonight: Breezy. Scattered showers in the evening, then occasional showers after midnight. Lows around 72 near the shore to around 54 near 5000 feet. Southeast winds 10 to 20 mph. Chance of rain near 100 percent.

Monday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 79 to 84 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

Lanai City

Rest Of Today: Mostly cloudy. Numerous showers and isolated thunderstorms in the morning, then numerous showers in the afternoon. Highs 72 to 80. Northwest winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 60 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 67. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 82. Northeast winds up to 15 mph. Chance of rain 30 percent.

Kaunakakai

Rest Of Today: Mostly cloudy. Breezy. Scattered showers and isolated thunderstorms in the morning, then numerous showers in the afternoon. Highs 70 to 88. East winds up to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Lows 60 to 76. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Partly sunny with isolated showers. Highs 71 to 89. East winds 10 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A statewide Flood Watch remains in effect through the day. Widely scattered showers, with occasional periods of heavy rain and isolated thunder, will likely occur through this evening. A drier, more typical breezy trade wind pattern will return from Monday onward.

Discussion

An upper level low from the north will be moving over the islands today. This low aloft will provide enough instability within a very moist resident air mass to justify a high probability of continued moderate to occasional bouts of heavy rain over the majority of the islands. The heaviest rain is occurring over eastern Maui this morning where it will not take much more rain to exacerbate flooding issues downslope of the Hanawi and Hana Reserves. Radar estimates of between 6 to 12 inches of rain have fallen over eastern Maui the past 36 hours. Due to very saturated grounds across both Oahu and Maui, relatively lower rainfall rates could initiate flooding across these islands.
Very little synoptic scale change to this unstable scenario warrants a higher awareness of return periods of moderate to strong rain intensity/rates that could persist into late evening. While instability indices remain low, the presence of the upper low within this saturated column (unseasonably high near 2.00 inch precipitable waters) will keep this mention of isolated thunder and localized heavy rain in place. Deep moisture with enhanced large scale lift brought on by the upper level low will keep the all-island Flood Watch in effect until 6 PM HST.
Trades will become locally breezy as ridging builds in northeast of the state the next couple of days. This will reinstate a tighter upstream pressure gradient and restrengthen trades. This wind pattern will focus the highest, most intense precipitation over windward mauka slopes. Wind sheltered leeward areas, such as the Kona slopes of Big Island, hold higher odds of getting into the intense rainfall action with possible isolated thunder today, especially if there are early day cloud breaks providing peeks of sun. As the upper low washes out southwest of the islands and surface ridging builds to the north into Tuesday, a breezy and increasingly stable trade wind regime is expected from Monday onward. Pockets of higher mid-level moisture riding in on trades will contribute to intermittent windward-exposed shower activity throughout next week. It appears the highest rainfall from a slug of passing mid layer moisture will likely drop the greatest areawide rainfall Thursday and/or Friday.

Aviation

The potential for heavy showers and thunderstorms will remain in the forecast as a broad upper low lingers over the region. Although the best chance for this activity will occur over windward and mauka locations with breezy trades returning today, some will manage to spill over or develop across leeward locations. Expect mountain obscurations above 2000 feet periodically for most windward locations today, especially over the eastern end of the state.
AIRMET Tango is posted for moderate turbulence between FL250 and FL450). Low-level turbulence downstream of island terrain is possible later today.
Light icing is possible between 120 and FL200 this morning due to thick layered mid-level clouds streaming from west to east over the eastern end of the state.

Marine

High pressure will build far northeast of the islands over the next couple of days as a front between the islands and the high gradually dissipates. Trade wind speeds will increase through today and remain fresh to locally strong for the next several days, primarily in response to the strengthening high, A Small Craft Advisory (SCA) remains in effect for waters around Maui County and the Big Island. A disturbance aloft will increase potential for heavy showers and thunderstorms today.
A medium period northeast swell will continue to decline for at least the next several days. However, the combination of strengthening trades and a small long period east swell from Tropical Cyclone Kristy may produce elevated surf along east facing shores for most of the new week. A small to moderate medium period north swell should arrive today and peak Monday, then gradually decline. A long period south swell will slowly decline over the next couple of days. A long period northwest swell arrive may arrive by Friday.

HFO Watches/Warnings/Advisories

Flood Watch through this afternoon for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kona, Kohala, Big Island Interior, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
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