West Side

Today: Sunny and breezy. Highs 75 to 87. Northeast winds 10 to 25 mph increasing to 20 to 25 mph in the afternoon.

Tonight: Mostly clear. Breezy. Lows 68 to 77. Northeast winds 10 to 20 mph.

Monday: Mostly sunny. Breezy. Scattered showers in the morning. Highs 75 to 87. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

South Side

Today: Sunny and breezy. Highs 77 to 89. Northeast winds up to 25 mph increasing to 15 to 25 mph in the afternoon.

Tonight: Clear and breezy. Lows 69 to 76. Northeast winds 10 to 20 mph.

Monday: Sunny and breezy. Highs 76 to 88. Northeast winds 10 to 25 mph.

North Shore

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 71 to 76 near the shore to around 57 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Central Maui

Today: Sunny and breezy. Highs 80 to 88. Northeast winds 10 to 25 mph.

Tonight: Mostly clear. Breezy. Lows 69 to 75. Northeast winds 10 to 20 mph.

Monday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 79 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Sunny. Highs 54 to 68. East winds up to 15 mph.

Tonight: Mostly clear. Breezy. Lows 42 to 56. East winds up to 20 mph increasing to 10 to 20 mph after midnight.

Monday: Breezy. Mostly sunny with scattered showers. Highs around 59 at the visitor center to around 61 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

East Maui

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 71 to 76 near the shore to around 57 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Lanai City

Today: Sunny and windy. Highs 70 to 82. Northeast winds 10 to 30 mph.

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows 64 to 70. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Sunny and breezy. Isolated showers in the afternoon. Highs 70 to 81. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Kaunakakai

Today: Sunny and breezy. Highs 68 to 88. Northeast winds 10 to 25 mph.

Tonight: Mostly clear. Breezy. Lows 59 to 75. Northeast winds 15 to 20 mph.

Monday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 68 to 87. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A ridge of high pressure will remain anchored in place north of the Hawaiian Islands for the foreseeable future. Easterly trade winds will continue to blow across the region through the end of this week. Shower activity will remain limited with brief increasing trends on Tuesday, and stronger trends from Thursday through Friday as a weak easterly wave moves from east to west across the state. Any showers will that develop in this trade wind pattern will favor windward mountain slopes of each island during the overnight to early morning hours.

Discussion

The satellite imagery this morning shows a weak easterly wave near 150W longitude riding the easterly trade winds towards the Big Island. This weak trough will bring a brief period of increasing shower trends to the state on Tuesday. Another stronger trough currently near 130W longitude, associated with the remnants of former tropical cyclone Douglas, will ride the trade winds into Hawaii from Thursday to Friday producing another round of showers spreading east to west across the state. Rainfall amounts with this first system will be limited due to the stable ridge aloft, the second trough will bring significant increases to humidity levels and the potential for higher rainfall amounts favoring island mountain slopes.
Otherwise, easterly trade winds will continue through the end of this week as the subtropical ridge remains locked in place north of Hawaii. Subtle day to day changes to the trade wind speeds should be expected. Mostly stable weather conditions are forecast for the next seven days with slight increases in shower activity on Tuesday, and stronger rainfall trends from Thursday through Friday as two easterly waves drift through the island chain. Rainfall amounts over the next seven days will remain limited due to large scale stability, with the highest amounts forecast during the Thursday to Friday time period.

Aviation

Moderate to locally breezy trades will continue through the holiday weekend, with a slight uptick in speed expected this afternoon. Low clouds and showers may continue to impact windward and mountain areas at times throughout the period, with some spillover showers into leeward sites possible as well, however VFR conditions are broadly expected, with localized MVFR possible mainly for windward sites.
AIRMET Sierra is in effect for mountain obscuration across windward sections of Oahu and the Big Island. This is expected to persist through the early morning, however the sporadic nature of shower activity may shift how long this AIRMET is in effect for.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of terrain for all islands. This AIRMET will likely continue through the weekend.

Marine

A high pressure ridge north of the Hawaiian Islands will remain nearly stationary this week and help drive moderate to strong trades across the local waters. A Small Craft Advisory (SCA), currently in effect for the typical windy waters and channels around Maui and the Big Island will be expanded by mid morning to cover all local Hawaiian waters. Moderate to locally strong trades and accompanying SCAs will continue through the week.
A new long period south-southwest swell, already being reported at the near shore buoys, will continue to fill in today. This will boost south shore surf heights to just shy of High Surf Advisory (HSA) levels through Monday. If this swell comes in much above guidance, a HSA will need to be issued. This swell will remain the primary south swell during the rest of next week as it gradually fades beginning on Tuesday.
Surf along east facing shores will remain rough and choppy through the forecast period as moderate to locally strong trades hold. Surf along north facing shores remains flat to tiny through much of this week.

HFO Watches/Warnings/Advisories

Small Craft Advisory from 6 AM this morning to 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, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov