West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 80 to 86. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 68 to 75. Northeast winds 10 to 25 mph with gusts to 50 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Windy. Isolated showers in the morning. Highs 79 to 86. Northeast winds 10 to 30 mph with gusts to 55 mph. Chance of rain 20 percent.

South Side

Today: Sunny and breezy. Highs around 89. Northeast winds 10 to 25 mph.

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

Friday: Sunny and breezy. Highs around 88. Northeast winds 10 to 25 mph with gusts to 50 mph.

North Shore

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 71 near the shore to around 52 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Gusts up to 40 mph. Chance of rain 70 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to around 65 near 5000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Gusts up to 45 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 81 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows 68 to 73. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 81 to 88. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Upcountry

Today: Windy. Mostly sunny with scattered showers. Highs around 61 at the visitor center to around 68 at the summit. East winds up to 30 mph. Chance of rain 50 percent.

Tonight: Windy. Partly cloudy with scattered showers. Lows 43 to 55. East winds up to 30 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 61 at the visitor center to around 69 at the summit. East winds up to 35 mph. Gusts up to 55 mph in the afternoon. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 71 near the shore to around 52 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Gusts up to 40 mph. Chance of rain 70 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to around 65 near 5000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Gusts up to 45 mph. Chance of rain 50 percent.

Lanai City

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 74 to 82. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows 63 to 68. Northeast winds 10 to 25 mph.

Friday: Mostly sunny. Windy. Highs 74 to 82. Northeast winds 10 to 30 mph.

Kaunakakai

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 72 to 88. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 59 to 75. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 72 to 88. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trade winds will become locally windy Friday into Saturday as high pressure north of the state strengthens and moves eastward. Showers will favor windward and mauka areas, and occasionally spill over to interior and leeward areas. Pockets of drier air filtering into the region, coinciding with the stronger winds, will introduce fire weather concerns Friday and Saturday. By Sunday into early next week, trades will gradually weaken and rain chances will increase due to the proximity of an upper-level low and deep moisture being drawn across the island chain.

Discussion

Early morning radar and satellite imagery depict scattered showers drifting into windward and mauka areas across the island chain, with the greatest coverage currently affecting windward Big Island. A broad surface high far northwest of the state will continue to drive locally breezy trade winds today, focusing clouds and passing showers along typical windward slopes and coasts. Leeward Big Island will once again see sea breeze development this afternoon, supporting isolated to scattered showers along leeward slopes before dissipating by evening.
An elongated upper-level trough edging in from the east will maintain slightly cooler temperatures aloft today through Saturday, allowing for an isolated thunderstorm or two to develop over the Big Island each afternoon. Elsewhere, the air mass should remain fairly stable.
The surface high to the northwest will strengthen and shift eastward along 30N through the weekend, tightening the local pressure gradient and producing a notable increase in trade wind speeds. Trades are expected to peak Friday into Saturday, with the windier locations potentially nearing Wind Advisory levels (sustained speeds around 30 mph). However, the high-res model guidance might be undershooting the wind speeds according to an ASCAT pass we received overnight, so winds may approach Wind Advisory criteria across the typical windier locations as early as later today.
Model guidance and upstream satellite imagery indicate a brief pocket of drier air moving in later today, followed by a band of moisture overnight and another dry pocket Friday into Saturday. These dry periods will coincide with the strongest winds, and while relative humidity values may be marginal, confidence is increasing that critical fire weather thresholds could be met Friday and Saturday, particularly over leeward and central zones and the drought-stricken Big Island North area. A Fire Weather Watch remains in effect for these areas from Friday morning through Saturday afternoon, with the highest concern expected during the late morning and afternoon hours each day when humidity is lowest. See the Fire Weather section below for additional details.
By late Saturday into Sunday, global models show a plume of deep tropical moisture being drawn northward across the islands, with precipitable water values projected to climb toward 2 inches. At the same time, an upper-level low is expected to separate from its parent trough to the east and retrograde westward near or over the state. Model guidance is coming into better agreement regarding its position and timing, increasing forecast confidence that its proximity will enhance instability, especially over the eastern half of the state. The combination of abundant moisture and colder mid-level temperatures will support a wetter and more unsettled trade wind pattern from late this weekend into early next week.
As the surface high continues eastward and weakens, the pressure gradient will ease, leading to a gradual reduction in trade wind strength to moderate to locally breezy levels Sunday through midweek next week.

Aviation

Moderate to breezy trades will persist today and could strengthen to locally strong on Friday. Stability will increase today as a mid-level trough currently over the Big Island is pushed eastward by a developing mid level ridge and drier air moves through. Small pockets of moisture moving along the trade wind flow will produce isolated MVFR conditions along windward slopes (primarily overnight), most likely on Big Island, while VFR will prevail elsewhere. A small pocket of moisture is possible late tonight into tomorrow morning and may bring a few extra MVFR showers to windward and mountain areas before drier and more stable air fills in Friday mid-morning.
AIRMET Tango will remain in place for low-level turbulence over and downwind of terrain.

Marine

A strengthening high pressure ridge north of the Hawaiian Islands will strengthen trade winds into the fresh to near gale force range through Saturday. The strongest winds in this range will develop in the channels and waters near Maui and the Big Island. A cold low pressure system moving into the Central Pacific basin this weekend will weaken this ridge, decreasing trade wind speeds rather significantly from Sunday onward. In the short term forecast, we expanded the coverage of the Small Craft Advisory to all waters due to the strengthening trade winds. This decision was supported by recent ASCAT wind initialization, increasing model guidance trends, and due to the building north-northwest swells that will increase significant wave heights to around 10 feet in some of our coastal waters through Saturday.
Today is a tale of two north-northwest (330 deg) swells, a moderate 11 to 13 sec period and a longer 15 to 17 sec period, moving through the Hawaii region today. The longer period swell will continue to build today and surf heights along north and west facing shores are forecast to strengthen into marginal High Surf Advisory (HSA) levels through the day. A HSA remains in effect for shores exposed to this north-northwest swell energy, including the north and west facing shores of Kauai, Niihau, Oahu, Molokai, and the north facing shores of Maui.
This long period north-northwest swell will continue to slowly weaken into a medium period swell from tonight into Friday, as another long period overlapping north-northwest swell builds into the region. Surf heights with this next swell will be similar or slightly higher than today's long period swell energy, possibly exceeding HSA thresholds along north and west facing shores from late Friday into Saturday.
Small background south swell energy will continue to keep surf along south facing shores above flat levels into early next week. Rough, choppy surf along east facing shores will continue through the forecast period and will see increasing trends into the weekend.

Fire weather

By later this morning, locally windy trades and decreasing moisture will begin increasing fire weather concerns. However, model guidance shows that another pocket of drier air will arrive Friday into Saturday, coinciding with the strongest trade wind speeds. Critical fire weather conditions will be possible during this time, with relative humidity values dropping into the low 40 percent range and trade winds reaching above sustained speeds of 20 mph. Since confidence is increasing, a Fire Weather Watch has been issued for leeward portions of all Hawaiian Islands, as well as interior sections of Oahu and the Big Island, from Friday morning through Saturday afternoon (though the greatest concern will be from late morning through the afternoon hours each day when relative humidity will be lowest). All of North Big Island has also been included in the Fire Weather Watch due to extreme drought conditions. See the latest Fire Weather Watch for additional details.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Fire Weather Watch from Friday morning through Saturday afternoon for Niihau, Kauai South, Kauai Southwest, East Honolulu, Honolulu Metro, Ewa Plain, Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains, Molokai North, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Lanai South, Lanai Mauka, Kahoolawe, Maui Leeward West, Maui Central Valley North, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island North, Kohala, Big Island Interior.
Small Craft Advisory until 6 PM HST Saturday for all Hawaiian waters,

Data Courtesy of NOAA.gov