Hilo

Tonight: Mostly cloudy with a 20 percent chance of showers. Lows 59 to 68 near the shore to 50 to 56 at 4000 feet. Light winds.

Monday: Partly sunny with a 20 percent chance of showers. Highs 76 to 82 near the shore to 62 to 69 at 4000 feet. Northeast winds up to 10 mph.

Monday Night: Partly cloudy with a 20 percent chance of showers. Lows 60 to 67 near the shore to 51 to 56 at 4000 feet. North winds up to 10 mph.

Kona

Tonight: Mostly cloudy. Lows around 69 near the shore to 44 to 50 near 5000 feet. Light winds.

Monday: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 80 to 86 near the shore to around 67 near 5000 feet. West winds up to 10 mph.

Monday Night: Mostly clear. A 20 percent chance of showers in the evening. Lows around 70 near the shore to 45 to 51 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. Light winds.

Monday: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 63 to 81. Northeast winds up to 10 mph.

Monday Night: Partly cloudy with a 20 percent chance of showers. Lows 60 to 69 near the shore to 53 to 60 near 3000 feet. Light winds.

Kohala

Tonight: Mostly cloudy. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. Light winds.

Monday: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 63 to 81. Northeast winds up to 10 mph.

Monday Night: Partly cloudy with a 20 percent chance of showers. Lows 60 to 69 near the shore to 53 to 60 near 3000 feet. Light winds.

South Big Island

Tonight: Mostly cloudy with a 20 percent chance of showers. Lows around 70 near the shore to around 49 near 5000 feet. Light winds.

Monday: Partly sunny. Slight chance of showers in the morning, then chance of showers in the afternoon. Highs around 81 near the shore to around 65 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 30 percent.

Monday Night: Partly cloudy with a 20 percent chance of showers. Lows around 71 near the shore to around 50 near 5000 feet. East winds up to 10 mph.

Puna

Tonight: Mostly cloudy with a 20 percent chance of showers. Lows 59 to 68 near the shore to 50 to 56 at 4000 feet. Light winds.

Monday: Partly sunny with a 20 percent chance of showers. Highs 76 to 82 near the shore to 62 to 69 at 4000 feet. Northeast winds up to 10 mph.

Monday Night: Partly cloudy with a 20 percent chance of showers. Lows 60 to 67 near the shore to 51 to 56 at 4000 feet. North winds up to 10 mph.

Waikoloa

Tonight: Partly cloudy. Lows around 70 near the shore to around 50 above 4000 feet. Light winds.

Monday: Mostly sunny. Highs 81 to 87 near the shore to 64 to 71 above 4000 feet. Northwest winds up to 10 mph.

Monday Night: Mostly clear. Lows 68 to 73 near the shore to around 51 above 4000 feet. Northeast winds up to 10 mph.

Detailed Forecast

Synopsis

A weak front near Kauai will move into Oahu tonight and will bring an increase of clouds with a few light showers. This frontal boundary is expected to dissipate near Maui on Monday. Otherwise, expect gentle trades to return on Tuesday gradually strengthening to moderate trades by middle of the week. A moderate trade wind pattern is expected for the rest of the week with mainly light showers possible over windward and mountain areas primarily during the overnight and early morning hours.

Discussion

Latest satellite imagery shows a weak frontal boundary near Kauai, which is producing some light showers over Kauai this afternoon. Overall the rainfall has been unimpressive with mainly just some light sprinkles over Kauai. This weak frontal boundary should move into Oahu tonight with some light rain showers possible. The frontal boundary is expected to dissipate as it moves near Maui on Monday, but a few light sprinkles will be possible over Maui as well on Monday. Over on the Big Island, we have a pocket of moisture that has been lingering over windward Big Island which will continue to produce some showers through tonight.
After the front dissipates, a weak high will build just north of the state on Tuesday and we should see gentle to moderate trade winds return across the state by Tuesday afternoon. Trades may strengthen a bit more Wednesday into Thursday, but generally a moderate trade wind pattern is expected during the second half of the week with some light passing showers over windward and mountain areas. Leeward areas should remain mostly dry with some light showers possible primarily during the overnight and early morning hours. Trade may strengthen a touch more Thursday into Friday with locally breezy trade winds possible.
For next weekend, global ensemble models are in fairly good agreement with trades gradually weakening as a ridge of high pressure moves closer to the state. Generally, fair weather should persist through next weekend.

Aviation

Light winds will keep sea and land breezes dominant through Monday. MVFR cigs are expected to continue affecting windward sections of the Big Island tonight, including PHTO, with some MVFR vsbys in showers possible at times. Conditions are forecast to improve around daybreak Monday. Elsewhere, a weak cold front will slide southward into Kauai this afternoon, into Oahu tonight, then fizzle out over Maui County on Monday. Some showers along with MVFR cigs/vsbys will be possible in windward areas in association with the frontal passage. Otherwise VFR conditions should prevail.
AIRMET Sierra remains in effect for mountain obscuration over windward sections of the Big Island and Kauai. The AIRMET may need to be expanded to include Oahu tonight.
AIRMET Tango remains in effect for moderate upper level turbulence between FL250 and FL410 over the entire state. Conditions should improve over Kauai by late this afternoon, but will likely remain in place across the remainder of the state through most of the night.

Marine

A weak front near Kauai this afternoon will shift slowly southeast down the island chain tonight and Monday before dissipating around Maui or the Big Island by Tuesday. Winds will remain light and variable during this time with land and sea breezes developing near the island coastlines. Isolated showers are expected preceding the frontal passage with gentle northerly winds behind the front. A weak area of high pressure will build in north of the islands around the middle of the week, bringing a return of light to moderate trade winds. By late Thursday, easterly trade winds look to gradually increase to the moderate to locally strong range.
The moderate medium-period northwest swell will keep High Surf Advisory (HSA) conditions through tonight before declining Monday. A HSA remains in effect through tonight for most north and west facing shores.
In addition, the small medium period north-northeast swell will gradually diminish over the next several days. A series of moderate- sized northwest swells will persist Monday night through the end of the week keeping surf elevated. A large long- period northwest swell is expected Friday and Saturday and peak surf heights could approach High Surf Warning levels.
Surf along east facings shores will remain small except shorelines exposed to the north-northeast swell through the first half of the week. Surf along south facing shores will remain tiny through the first half of next week with mainly background energy.

Fire weather

KBDI values remain elevated across leeward areas and no significant leeward rainfall is anticipated for the next week. Although not much rainfall is expected with the weak front, it should bring an increase of humidities and will keep the humidities above the critical thresholds over the next few days. We are starting to get to the time of year, where it is harder to reach critical fire weather thresholds due to the cooler day time temperatures helping to keep the humidities from dropping below 45%. Critical fire weather is not anticipated this upcoming week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.

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Data Courtesy of NOAA.gov