West Side

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 75 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Isolated showers after midnight. Lows 66 to 75. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Sunny and breezy. Isolated showers in the morning. Highs 76 to 89. East winds 10 to 25 mph. Chance of rain 20 percent.

South Side

Today: Sunny and breezy. Highs 77 to 90. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Mostly clear. Lows 68 to 73. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight.

Saturday: Sunny and breezy. Highs 79 to 90. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

North Shore

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 80 to 87 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows around 72 near the shore to around 54 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 80 to 87 near the shore to around 67 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Breezy. Scattered showers in the morning. Highs 81 to 88. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Breezy. Lows 68 to 73. East winds 10 to 20 mph.

Saturday: Sunny and breezy. Highs 82 to 90. East winds 10 to 25 mph.

Upcountry

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 64 at the visitor center to around 67 at the summit. East winds up to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows around 48 at the visitor center to around 46 at the summit. East winds up to 25 mph. Chance of rain 20 percent.

Saturday: Sunny and breezy. Isolated showers in the morning. Highs around 64 at the visitor center to around 66 at the summit. East winds up to 25 mph. Chance of rain 20 percent.

East Maui

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 80 to 87 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows around 72 near the shore to around 54 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 80 to 87 near the shore to around 67 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs 70 to 81. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 60 to 67. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight.

Saturday: Sunny. Highs 72 to 81. East winds 10 to 15 mph.

Kaunakakai

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs 70 to 89. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 60 to 74. East winds 10 to 15 mph.

Saturday: Sunny and breezy. Highs 71 to 90. East winds 10 to 25 mph.

Detailed Forecast

Synopsis

A high pressure ridge will build north of the Hawaiian Islands lasting into early next week. Expect stable trade winds with brief passing showers and breezy winds through at least Tuesday. Shower activity will favor windward slopes, and aside from afternoon showers over the Kona slopes of the Big Island, leeward areas will remain mostly dry.

Discussion

The satellite imagery this morning shows fairly stable clouds riding into the windward slopes of each island on the trade winds. These clouds will not produce much shower activity due to the stable conditions created by a high pressure ridge aloft, shown on 500 mb streamlines. Subsidence temperature inversion heights will remain in the 5,000 to 6,000 foot elevation range today in a fairly dry environment. Brief passing showers are possible in this stable boundary layer, mainly over windward and mountain areas in the overnight to early morning hours.
A broad high pressure ridge will remain locked in place north of the state through much of next week. Moderate to breezy easterly trade winds will continue during this extended forecast time period. The interaction of the breezy trade wind flow with the islands should generate wind gusts around 40 mph over and downwind of terrain, though isolated areas on the Big Island and Maui County could approach Wind Advisory criteria at times. The GFS and ECMWF are showing no distinct organized areas of shower activity or instability. This will limit windward rainfall activity into the isolated to scattered range over windward and the Kona slopes of the Big Island with dry conditions continuing over leeward areas. See the Fire Weather section below for additional discussion. A slight decrease in trade winds is expected Wednesday.

Aviation

A high pressure ridge will strengthen north of the state over the next several days producing moderate to breezy trade winds. A fairly stable environment will keep only brief passing showers in the forecast into the weekend.
AIRMET Tango has been issued today for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely persist into the weekend as breezy trades continue.

Marine

High pressure to the north will strengthen, causing strong trade winds to develop through the weekend and into the beginning of next week. The high will then weaken slightly next week, causing trade winds to marginally decrease into the breezy to locally strong range by the later half of next week. The current Small Craft Advisory has been expanded in coverage to include the rest of the channels and is in effect through the weekend. It will likely be extended into next week if trade winds remain strong.
Surf for south facing shores will gradually decline through the weekend below the summertime average as the current S swell declines. Tiny, long period S swells will then hold into next week until a new small long period swell looks to fill in by Tuesday night. This new swell could boost surf heights near the summertime averages (5 ft) by the middle of next week.
Surf for east facing shores will increase this weekend and become more rough and choppy as trade wind speeds increase and the north shore surf will remain seasonally tiny.

Fire weather

Breezy, gusty, and rather dry conditions will develop on Saturday and persist into early next week. Relative humidity at lower leeward elevations will likely fall below 45 percent each afternoon, and with the inversion dropping to as low as 5,000 feet winds will become gusty over and downwind of terrain. This will result in near critical fire weather conditions over dry leeward areas, though no headlines (watches or warnings) are due since the Keetch Byram Drought Index will remain below the 600 threshold at Honolulu.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov