Hilo

Tonight: Partly cloudy. Isolated showers after midnight. Lows 57 to 66 near the shore to 47 to 53 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 78 near the shore to 61 to 67 at 4000 feet. West winds up to 10 mph shifting to the east in the afternoon. Chance of rain 30 percent.

Wednesday Night: Mostly cloudy with isolated showers. Lows 58 to 67 near the shore to 48 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Kona

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 68 near the shore to 42 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the afternoon. Highs 80 to 85 near the shore to around 64 near 5000 feet. South winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Lows around 69 near the shore to 43 to 50 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy. Isolated showers in the evening. Lows 58 to 67 near the shore to 50 to 57 near 3000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 40 percent.

Kohala

Tonight: Partly cloudy. Isolated showers in the evening. Lows 58 to 67 near the shore to 50 to 57 near 3000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 40 percent.

South Big Island

Tonight: Partly cloudy. Lows around 70 near the shore to around 49 near 5000 feet. Northeast winds up to 10 mph.

Wednesday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 64 near 5000 feet. Northeast winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Wednesday Night: Mostly cloudy. Lows around 71 near the shore to around 51 near 5000 feet. Northeast winds 10 to 15 mph.

Puna

Tonight: Partly cloudy. Isolated showers after midnight. Lows 57 to 66 near the shore to 47 to 53 at 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 78 near the shore to 61 to 67 at 4000 feet. West winds up to 10 mph shifting to the east in the afternoon. Chance of rain 30 percent.

Wednesday Night: Mostly cloudy with isolated showers. Lows 58 to 67 near the shore to 48 to 54 at 4000 feet. Light winds. Chance of rain 20 percent.

Waikoloa

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 66 to 72 near the shore to 45 to 51 above 4000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 20 percent.

Wednesday: Partly sunny. Highs around 82 near the shore to 63 to 68 above 4000 feet. East winds up to 10 mph shifting to the northwest in the afternoon.

Wednesday Night: Mostly cloudy. Lows 67 to 73 near the shore to 46 to 51 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

A cold front will move across Kauai and Oahu tonight into early Wednesday, then stall across the central islands late Wednesday through Thursday. This will bring periods to showery weather to most islands this week. More unsettled weather is possible Friday through the weekend as a plume of deep moisture develops along another front as an upper-level disturbance moves across the state. Drier weather and improving conditions are then expected early next week as ridging builds across the region.

Discussion

Satellite imagery shows a cold front approximately 100 miles west- northwest of Kauai this afternoon. Moisture ahead of the front is resulting in pockets of clouds and showers across the western islands. Elsewhere, localized sea breezes due to light to moderate east-southeasterly flow is producing some clouds over island interiors. Expect little change through this evening.
Guidance continues to show the front moving towards the state this afternoon, then across Kauai late this evening and Oahu by early Wednesday morning. The progressiveness of the front should slow considerably later tonight as the mid-level flow becomes parallel to the front. Nonetheless, expect an uptick in clouds and showers across the western islands tonight into early Wednesday, with breezy northerly winds developing in the wake of the front.
Guidance then shows the front stalling over the central islands late Wednesday through Thursday as a shortwave trough moves overhead. The will help to maintain clouds and showers across most islands, with some enhanced showers possible over windward and mauka areas of Oahu and Maui County.
Late in the week and over the weekend, the model solutions, their ensembles, as well as the AI versions of both the GFS and ECMWF suggest some more uncertainty in the forecast. Overall, the pattern appears to favor a somewhat unsettled period as moisture pulls along the stalled out frontal boundary and upper level troughing moves overhead. Improving conditions are then forecast for early next week as deep layer ridging builds over the island chain.

Aviation

Light to moderate east-southeasterly winds will keep a land and sea breeze pattern in place in advance of a cold front that is expected to reach Kauai late this evening, Oahu early Wednesday morning, and then stall out somewhere over the central part of the state. Showers are expected to increase near the frontal boundary, with breezy northerly winds in its wake. Mainly VFR conditions will prevail in advance of the front, then some brief MVFR cigs/vsbys could develop near the frontal boundary in showers.
AIRMET Tango is in effect for moderate upper level turbulence between FL310 and FL370 due to jet stream winds. AIRMET Sierra may be needed for mountain obscuration for Kauai and Oahu overnight.

Marine

Gentle southerly winds will give way to a front that will produce a brief period of fresh to strong northerly winds and elevated rough seas around Kauai tonight. North to northeast winds associated with the front will weaken as the feature passes over Oahu on Wednesday then stalls across Maui County waters Wednesday night. Around the Big Island, expect continued gentle east to southeast winds. A Small Craft Advisory (SCA) has been issued for waters around Kauai for tonight, and although we do not anticipate expanding the SCA, there is some chance it could be issued for Oahu waters on Wednesday morning. A surface ridge will develop about 100 nm north of Kauai on Thursday, leading to gentle to moderate easterly trade winds through at least Friday. Winds will turn out of the southeast and south during the weekend as another front approaches. A disturbance aloft could trigger heavier showers and possibly thunderstorms during this time.
Overlapping west-northwest to north-northwest swells will produce surf around High Surf Advisory (HSA) levels for exposed north and west facing through Friday. The latest west-northwest swell is filling in around Kauai and Oahu this afternoon after building to around 6 to 7 feet at 14 to 15 seconds at the NOAA buoys northwest of Kauai today. Expect this swell to generate surf just below HSA levels along north and west shores of Kauai and Oahu during its peak tonight, with gusty winds along the front producing rough conditions on Kauai and possibly on Oahu closer to daybreak. Overlapping pulses of west-northwest swell, similar in size, will arrive later Wednesday and keep surf near advisory levels, mainly on Kauai and Oahu, through Friday. A sharp downward trend and shift out of the north-northwest is expected during the weekend, followed by a potentially large northwest swell next Tuesday.
East shore surf will remain below seasonal average through the week, though a brief increase is possible on Kauai tonight due to strong northerly winds behind the front. Surf along south facing shores will remain very small through the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel.

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Data Courtesy of NOAA.gov