Hilo

Tonight: Frequent showers. Locally heavy rainfall possible in the evening. Lows 62 to 70 near the shore to 53 to 60 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Friday: Cloudy with frequent showers. Highs 76 to 82 near the shore to 63 to 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 90 percent.

Friday Night: Cloudy with showers. Lows 61 to 69 near the shore to 50 to 58 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 90 percent.

Kona

Tonight: Mostly clear. Lows around 72 near the shore to 47 to 53 near 5000 feet. Northeast winds up to 10 mph in the evening becoming light.

Friday: Mostly sunny. Highs 83 to 88 near the shore to around 69 near 5000 feet. Light winds.

Friday Night: Mostly clear. Lows around 72 near the shore to 45 to 52 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy. Breezy. Showers likely in the evening, then scattered showers after midnight. Lows 63 to 71 near the shore to 56 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs around 78 near the shore to 68 to 77 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Friday Night: Breezy. Mostly cloudy with scattered showers. Lows 62 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy. Breezy. Showers likely in the evening, then scattered showers after midnight. Lows 63 to 71 near the shore to 56 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs around 78 near the shore to 68 to 77 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Friday Night: Breezy. Mostly cloudy with scattered showers. Lows 62 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 74 near the shore to around 53 near 5000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Highs around 85 near the shore to around 69 near 5000 feet. East winds 10 to 20 mph.

Friday Night: Mostly clear. Breezy. Lows around 73 near the shore to around 51 near 5000 feet. East winds 10 to 20 mph.

Puna

Tonight: Frequent showers. Locally heavy rainfall possible in the evening. Lows 62 to 70 near the shore to 53 to 60 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Friday: Cloudy with frequent showers. Highs 76 to 82 near the shore to 63 to 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 90 percent.

Friday Night: Cloudy with showers. Lows 61 to 69 near the shore to 50 to 58 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 90 percent.

Waikoloa

Tonight: Mostly clear. Lows around 73 near the shore to around 54 above 4000 feet. East winds up to 10 mph.

Friday: Sunny. Highs 81 to 88 near the shore to 67 to 72 above 4000 feet. Northeast winds up to 10 mph.

Friday Night: Mostly clear. Lows around 72 near the shore to 49 to 54 above 4000 feet. East winds up to 10 mph.

Detailed Forecast

Synopsis

Trade winds will decrease tonight into the weekend as high pressure north of the state weakens. Expect fairly dry conditions into the first half of next week. An upper low southwest of the islands will enhance showers across eastern slopes of the Big Island through Friday morning.

Discussion

The pressure gradient between high pressure to our north and surface troughing to our southwest has begun to slacken, resulting in slightly weaker trade winds this afternoon. As a result, the Wind Advisory is cancelled. Satellite loop shows patchy broken to overcast low clouds embedded within this flow piling up across windward shores and slopes of the smaller islands east of Kauai. The northern edge of an area of more extensive low cloud cover lies across the Big Island, where broken to overcast low clouds cover most windward and southeast shores and slopes. In contrast, Kauai has scattered low clouds to mostly clear skies. Radar shows scant shower activity, with the bulk associated with the more pervasive cloud cover over and south of the Big Island. Afternoon soundings show a contrast between the western and eastern ends of the main island chain, thanks to an upper low and associated surface troughing southwest of the islands. PW ranges from less than an inch over Kauai to almost 1.7 inches over the Big Island. Both soundings depict positive airmass stability, but with conditions over Kauai much more so. A strong inversion is noted near 6700 feet in the Lihue sounding, which acts to cap vertical cloud development and shower activity. This inversion is weaker on the Hilo sounding.
Models show trade wind speeds will continue to decrease, slightly at first, through tonight, enough to cancel the Wind Advisory. Expect decreasing wind speeds into the weekend. Light and variable winds return by next week, from late Monday into Wednesday, as two passing fronts push into the ridge north of the island chain. Rainfall will be limited, with dry conditions likely persisting into Wednesday. Two exceptions to this dry pattern will be enhanced showers along the eastern slopes of the Big Island lasting into Friday morning, and a slight boost in trade wind showers for windward and mountain areas of all islands, due to a passing short wave trough, from Saturday night to Sunday morning. Models show a weakening front drifting towards the islands by the end of next week, possibly bringing our next best chance for rainfall coverage.

Aviation

Strong trade winds will continue through this evening, then become breezy to locally strong overnight into Friday. AIRMET Tango remains in effect for moderate low-level turbulence to the lee of the terrain of all islands. AIRMET Tango for strong surface winds near 30 kt will continue through this evening.
Low clouds and showers will continue to favor windward and mauka areas. An increase in moisture will bring an elevated chance of MVFR conditions and tempo mountain obscurations to windward Big Island tonight. Otherwise, expect main VFR across the islands, with local MVFR over windward and mauka areas.

Marine

High pressure centered far northeast of the Hawaiian Islands will gradually weaken over the next several days, with trade winds diminishing to moderate to locally fresh speeds through the weekend. An ASCAT pass this afternoon revealed no more gale-force winds around Maui County and the Big Island and weakening winds elsewhere. Therefore, the Gale Warning for the windier waters around Maui County and Big Island and the Small Craft Advisory (SCA) has been downgraded to a Small Craft Advisory through Friday afternoon, while the SCA for the remaining waters is now cancelled. Winds are forecast to become light and variable by early next week as a front approaches the state from the northwest.
Elevated surf along north and west shores will hold through tonight with a subtle fall Friday and more significant drop this weekend as the current north-northwest swell declines. A much larger, long- period northwest swell, originating from a deep hurricane force low developing over the northwest Pacific later this week, is scheduled to reach the islands sometime around the middle of next week. This swell will likely bring surf along north and west facing shores to high surf warning levels late next week. Rough, choppy surf will continue along east facing shores through Friday in response to the recent and ongoing strong trades, then subside this weekend as the trades fall off.

Fire weather

As winds decrease below critical threshold and relative humidity rebounds, the threat of dangerous fire weather has diminished and the Red Flag Warning (RFW) has been cancelled. While rather dry weather is expected through much of the forecast period, wind speeds and relative humidity will remain outside critical fire weather thresholds through the forecast period.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Big Island Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Big Island Helicopter Tours today!

Data Courtesy of NOAA.gov