Hilo

Today: Mostly sunny with scattered showers in the morning, then cloudy with occasional showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 76 to 82 near the shore to 63 to 69 at 4000 feet. North winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy with showers likely and slight chance of thunderstorms in the evening, then partly cloudy with isolated showers after midnight. Lows 58 to 66 near the shore to 45 to 51 at 4000 feet. Light winds. Chance of rain 70 percent.

Friday: Mostly sunny with scattered showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs 76 to 81 near the shore to 60 to 66 at 4000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Sunny with isolated showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 80 to 86 near the shore to around 65 near 5000 feet. Northwest winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms in the evening, then partly cloudy with isolated showers after midnight. Lows around 67 near the shore to 38 to 46 near 5000 feet. Light winds. Chance of rain 40 percent.

Friday: Mostly sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs 79 to 85 near the shore to around 62 near 5000 feet. Light winds becoming west around 10 mph in the afternoon. Chance of rain 40 percent.

Waimea

Today: Sunny in the morning, then mostly cloudy with showers likely and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 60 to 83. North winds 10 to 15 mph shifting to the northwest in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms in the evening, then partly cloudy with isolated showers after midnight. Lows around 59 near the shore to 48 to 56 near 3000 feet. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Friday: Mostly sunny with scattered showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs 57 to 81. Light winds becoming north around 10 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Sunny in the morning, then mostly cloudy with showers likely and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 60 to 83. North winds 10 to 15 mph shifting to the northwest in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms in the evening, then partly cloudy with isolated showers after midnight. Lows around 59 near the shore to 48 to 56 near 3000 feet. Northwest winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Friday: Mostly sunny with scattered showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs 57 to 81. Light winds becoming north around 10 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Breezy. Mostly sunny with scattered showers in the morning, then mostly cloudy with showers likely and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 80 near the shore to around 64 near 5000 feet. Northwest winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms in the evening, then partly cloudy with isolated showers after midnight. Lows around 67 near the shore to around 42 near 5000 feet. North winds up to 10 mph. Chance of rain 50 percent.

Friday: Sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 79 near the shore to around 61 near 5000 feet. Light winds. Chance of rain 40 percent.

Puna

Today: Mostly sunny with scattered showers in the morning, then cloudy with occasional showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 76 to 82 near the shore to 63 to 69 at 4000 feet. North winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy with showers likely and slight chance of thunderstorms in the evening, then partly cloudy with isolated showers after midnight. Lows 58 to 66 near the shore to 45 to 51 at 4000 feet. Light winds. Chance of rain 70 percent.

Friday: Mostly sunny with scattered showers in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs 76 to 81 near the shore to 60 to 66 at 4000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 79 to 85 near the shore to around 65 above 4000 feet. Northwest winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers and slight chance of thunderstorms in the evening, then partly cloudy with isolated showers after midnight. Lows 62 to 70 near the shore to 38 to 49 above 4000 feet. Light winds becoming east around 10 mph after midnight. Chance of rain 40 percent.

Friday: Sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs 78 to 85 near the shore to 60 to 66 above 4000 feet. Light winds becoming northwest 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Light northerly winds are expected today with low pressure several hundred miles northeast of the state. A disturbance aloft supporting the low will bring spotty heavy downpours and a chance of thunderstorms today, particularly near a stalled surface trough near the Big Island. Somewhat stable and mostly dry conditions will prevail Friday through Sunday, as the light background winds gradually become east and southeast. Chances for rainfall increase Monday as a front approaches from the northwest.

Discussion

Made a few tweaks to the PoPs and supporting grids for this afternoon and evening to boost some rain chances to be in better agreement with some of the high resolution model guidance and national blend of models. No other significant changes in the near term. For the longer term, winds early next week have been trending downward in the last couple of runs of both the GFS and ECMWF, so have nudged the forecast downward.
No changes to the weather features impacting our weather. A surface trough remains near the Big Island, a low pressure system is north-northeast of the islands, and a cold front is off to the northwest. An upper level trough is moving over the islands, and will help provide some instability to the region today and into tonight.
Light northerly winds are starting to spread across the islands early today. With light winds, expect some afternoon sea breezes to set up. Satellite derived precipitable water (PW) shows the highest values over portions of the Big Island and areas to the southeast. There is another pocket of moisture over Kauai which will likely spread eastward some today.
Despite the limited moisture, as the upper level trough moves over the islands, there could be enough instability to trigger some heavier showers or thunderstorms. Models continue to show 500mb temperatures getting down to -15C over the smaller islands today, which is below normal, and down to around -10 over the Big Island which is near normal. The most likely time for heavier showers or thunderstorms will be this afternoon over all the islands, and into the evening hours on the Big Island.
There is a chance for some winter weather to reach the Big Island summits this afternoon, particularly if a thunderstorm develops over the interior of the islands. Have held off on issuing any Winter Weather Advisories as the chance for a more organized event remains low. There is also the potential for frozen precipitation, mostly likely in the form of freezing rain, on the highest reaches of Haleakala if a heavy shower or thunderstorm were to develop there.
A Wind Advisory remains in effect for the Big Island summits today. Winds have slowly trending upwards overnight. Anticipating the peak of the winds to be this morning, with a downward trend this afternoon and evening.
Stable and drier conditions will return for most of the state Friday into the weekend. The upper level and surface troughs will slowly move eastward as drier conditions fill in on Friday. Interior Big Island could see isolated downpours and thunderstorms Friday afternoon, but elsewhere rainfall should be limited. Light northerly winds will veer easterly on Saturday and southeasterly on Sunday, with only isolated afternoon showers expected.
Another round of unsettled weather is possible on Monday as an upper level trough sends a front across the state.

Aviation

Developing land breezes and relatively stable conditions will support VFR through the morning. An upper trough will advance across the area reaching the Big Island this afternoon, outrunning the better low-level moisture over the smaller islands. Thus, while the chance for spotty heavy showers/isolated t-storms will increase over island interiors during the day, coverage is expected to remain limited. Land breezes will once again bring clearing conditions on Thursday evening. For the Big Island, interaction between the approaching upper trough and the existing moisture along the resident trough axis will set the stage for a greater coverage of heavy showers and pockets of thunderstorm activity on Thursday afternoon.
AIRMET Sierra for mountain obscuration may be needed over east and southeast-facing slopes of the Big Island this afternoon.
AIRMET Tango for moderate upper-level turbulence may be needed by midday.

Marine

Light northerly winds will continue over the next couple of days as a deepening low persists about 650 miles northeast of Hawaii. The low will send a moderate northeast swell across the islands that will build today and continue through Sunday, peaking Friday night and early Saturday. An upper trough is currently moving over the state and is expected to bring a slight chance of thunderstorms for the coastal waters through tonight. Both features will move out Friday with more stable trades building in. A front will approach the islands from the northwest early next week with easterly winds mainly staying light through the weekend.
A new northwest swell is expected to arrive later today and tonight and, in tandem with the pulse from the northeast, could increase surf to advisory level for north facing shores by Friday morning. Both swells will drop over the weekend with another large northwest swell forecast to arrive early Tuesday next week. Small background south swell will continue into next week.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for Big Island Summits.

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Data Courtesy of NOAA.gov