Hilo

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 60 to 68 near the shore to 49 to 56 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 82 near the shore to 63 to 68 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 60 to 68 near the shore to 49 to 57 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Kona

Tonight: Partly cloudy with isolated showers. Lows around 70 near the shore to 43 to 50 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 81 to 86 near the shore to around 68 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to 44 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Partly cloudy with isolated showers. Lows 60 to 70 near the shore to 52 to 59 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 63 to 81. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday Night: Breezy. Partly cloudy with isolated showers. Lows 61 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Kohala

Tonight: Breezy. Partly cloudy with isolated showers. Lows 60 to 70 near the shore to 52 to 59 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 63 to 81. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday Night: Breezy. Partly cloudy with isolated showers. Lows 61 to 70 near the shore to 54 to 61 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Lows around 71 near the shore to around 49 near 5000 feet. Northeast winds up to 15 mph.

Monday: Mostly sunny. Highs around 84 near the shore to around 67 near 5000 feet. East winds up to 15 mph.

Monday Night: Partly cloudy. Breezy. Lows around 72 near the shore to around 50 near 5000 feet. Northeast winds 10 to 20 mph.

Puna

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 60 to 68 near the shore to 49 to 56 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 82 near the shore to 63 to 68 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 60 to 68 near the shore to 49 to 57 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly clear. Lows 67 to 73 near the shore to 46 to 52 above 4000 feet. Southeast winds up to 15 mph.

Monday: Sunny and breezy. Highs 81 to 87 near the shore to 65 to 72 above 4000 feet. Northeast winds up to 20 mph.

Monday Night: Mostly clear. Lows 69 to 74 near the shore to 48 to 53 above 4000 feet. East winds up to 15 mph.

Detailed Forecast

Synopsis

Light to moderate easterly trades will gradually strengthen into the breezy to strong range by midweek as high pressure strengthens to the north, with brief passing showers favoring windward and mountain areas. An upper level low passing just south of the islands may enhance rainfall coverage over the eastern half of the state Friday into the weekend, with trades gradually subsiding into the moderate to breezy range.

Discussion

Current visible satellite imagery and surface observations show some low clouds moving into windward areas on the light to moderate trades and additional cloud build up over leeward interiors with sea breeze activity this afternoon. As an approaching front dissipates and high pressure builds to our north, trades will gradually strengthen tonight through mid week. The latest model guidance suggests that the strongest winds speeds will impact the state Wednesday into Thursday as trades become breezy to strong, with Wind Advisory conditions possible for the typical windier areas. Wind speeds at the Big Island summits are expected to jump up to warning levels as early as tomorrow morning as an upper level jet streak dives down over the area. As such, a High Wind Warning has been issued for the summits starting tomorrow at 6 AM HST.
Fairly dry and stable conditions will persist for the first half of the week before a combination of upper level dynamics and low level moisture edging up from the tropics begin to increase the rain chances for windward areas across the eastern end of the state. Model guidance continues to show an upper level low pinching off from the main trough southeast of the island chain and then retrograding westward, potentially bringing increased instability that could help to enhance trade wind showers across the Big Island. However, there are still some model discrepancies concerning that upper level feature, so forecast confidence on potential impacts (mostly rainfall potential) is on the lower side for now. Stay tuned for forecast updates.

Aviation

VFR conditions will dominate as trade winds gradually strengthen through Monday. Somewhat dry weather will persist, with only isolated areas of MVFR conditions in -SHRA along terrain, mainly on windward Big Island and Kauai. With trades on the rise, AIRMET Tango for tempo moderate low level turbulence over and downwind of terrain could be needed as early as Monday.
An upper level trough and an accompanying jet stream will develop just north then east of the islands tonight and Monday. The jet stream may produce moderate to severe turbulence above FL250 just northeast of the islands tonight, while AIRMET Tango for moderate turbulence aloft will likely be needed over the state after midnight.

Marine

Easterly trade winds will strengthen to moderate to locally strong overnight. A Small Craft Advisory (SCA) has been issued to address the freshening winds. Initially, SCA conditions should be limited to the windier waters around Maui County and the Big Island, but by Tuesday, the advisory will likely need to be expanded to include most Hawaiian waters due to the combination of stronger winds and building seas. SCA conditions are expected within Hawaiian coastal waters throughout the coming week and possibly beyond.
A series of overlapping north-northwest swells are expected to push surf heights to near advisory levels on Monday and Tuesday. A gradual downward trend is expected to follow, but surf along north and west facing shores could remain elevated through the weekend.
Surf along south-facing shores will remain up through Monday due to an out-of-season south swell, which will gradually subside Tuesday. Seasonal conditions will return around midweek with a mix of smaller southeast and south-southwest swells.
Surf along east-facing shores will increase through midweek due to strengthening trade winds both locally and upstream of the Islands.

Fire weather

Critical fire weather conditions are not anticipated this evening as wind speeds and relative humidity values aren't anticipated to approach critical levels. For the rest of the week, the main concern will be the strengthening trades, which current model guidance suggests will peak around Wednesday, likely exceeding critical thresholds. Relative humidity values look to be the limiting factor next week, but could still drop below 50 percent during the windier periods.

HFO Watches/Warnings/Advisories

High Wind Warning from 6 AM to 6 PM HST Monday for Big Island Summits.
Small Craft Advisory from midnight tonight to 6 PM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov